The 2016 NIGMS Cell Day chat was held on Thursday, November 3, 2016, from 10 a.m. to 3 p.m. EDT. Scientists from across the Institute answered questions from students, teachers and the general public.
Good morning and welcome to Cell Day 2016! We are ready for your questions.
Coppell Middle School North, Texas: Can you explain myelin a bit? Amicia Elliott: Sure, thanks for the question! Myelin is a fatty material that acts like insulation around a wire. Although insulation continues down an entire wire, there are regular gaps in myelin called nodes of Ranvier. Electrical nerve impulses speed across myelin in leapfrog fashion, powering up and launching again at each node of Ranvier. This material is a critical part of nerve cell function and the speed of transferring information along a given network of nerve cells.
Coppell Middle School North, Texas: Are there more cells than the ones we learn about? Jacob Nordman: There sure are! There is something called the microbiome that includes a heterogeneous population of bacterial cells that have a symbiotic relationship with our body. They help maintain body health in a variety of ways, and the majority of them are uncharacterized.
Additionally, there is belief that the number of cell types in the brain are far more varied than previously thought. Usually brain cells are divided along metabolic and neurotransmitter releasing properties, but there is increasing belief that there are brain cell types that can be defined exclusively by their morphological (structural) properties, and that these properties may help reveal unique functions helpful for brain function. These are also only beginning to be explored.
Coppell Middle School North, Texas: Why do plants and animals need to have different types of cells? Kristine Willis: Hi North Science! Great question. Plants and animals need to have different kinds of cells because they have different lives. For example, animals can move around to find food, which gives them energy; but plants have to stay in one place and make their own energy from the sun. Plants have special cell parts called chloroplasts that make energy from sunlight. Animals don't have chloroplasts.
Marriotts Ridge, Maryland: What would happen if brain cells divide too quickly?Janna Wehrle: Like other cells, brain cells divide at different speeds at different times in an organism's life. But when cells are dividing faster than they should be, they are often not perfectly formed and can cause a tumor.
Souhegan High School, New Hampshire: How do I get to the podcast? OCPL Team19: If you mean the Facebook Live post, please visit,
www.facebook.com/nigms.nih.gov. Keep the questions coming!
River Terrace Education Campus, District of Columbia: What do cells have to do with our dna?
Michael Bender: Cells have a lot to do with our DNA! Cells have an important role in maintaining the DNA, making accurate copies of the DNA when cells divide, and allowing the appropriate expression of genes from the DNA.
Marriotts Ridge, Maryland: What other eukaryotic cells besides red blood cells doesn't have a nucleus? Alison Gammie: Great question. The only two types of human cells that don't have a nucleus are red blood cells and blood platelets.
Mountlake Terrace High School, Washington: Why don't neurons reproduce? Paul Sammak: There are neuronal progenitor cells that do reproduce in parts of the brain. In the adult, there are neuronal precursors that are always forming new neurons, especially in olfactory structures and hippocampus. Once neurons are terminally differentiated and interconnect to neighbors, they change their genetic expression pattern to suppress cell division. The interconnected network of neurons needs a bit of stability to control your body in defined ways, so it might be a good thing that your brain is reticent to undergo too much cell division.
G. Holmes Braddock Senior High School, Florida: I've heard that we all host cancerous cells in our bodies that are dormant within us. Is this true? If so, what causes them to activate? Jessica Faupel-Badger: Good morning Braddock HS and thanks for this question! Cancer is a multistep process. It is possible there are cells that have acquired mutations but have not divided enough to be detectable. These cells could receive signals from hormones or growth factors that then stimulate the cells to divide. The body's immune response may also be keeping these cells in check but cancer cells can develop mechanisms to overcome the immune response. These are some reasons why it may take a long time before a cancer is detectable.
Coppell Middle School North, Texas: What would happen if there was no Eukaryotic and Prokaryotic cells but just one type of cell that had the same characteristics as Eukaryotic and Prokaryotic? Shiva Singh: We don't know for sure, but having different kinds of cells is the Nature's way to endow plants and animals to adapt and thrive under diverse environmental conditions.
Coppell Middle School North, Texas: What organelle do you think is the most useless in the cell? and why? Amicia Elliott: Thanks for the interesting question! In my opinion, this definitely depends upon the type of cell. Most cells have just the right number of organelles to perform their functions. I will say that if you look at red blood cells, the nucleus is the most useless in the cell because a mature red blood cell lives, fully functionally, without one.
G. Holmes Braddock Senior High School, Florida: Can Stem cell therapy help children with Autism? Susan Haynes: Hi Braddock High, That's a good question. Scientists are working hard to understand the causes of autism and how children with autism differ from those who don't have it. And the other consideration is that autism isn't a single condition, but rather spans a range of conditions that differ in severity. So it's possible that sometime in the future scientists will understand enough about the disease to know exactly what goes wrong and to develop effective stem cell therapies.
Check your cell IQ! Which organelle is known as "the cell's brain"?
Coppell Middle School North, Texas: Would it be possible for a white blood cell to get over run by bacteria and not be able to keep our body healthy?Alison Cole: The
blood has several types of
cells including neutrophils, bands, eosinophils, basophils, monocytes and lymphocytes. Each fights infection in a different way. Neutrophils, for example, are one of the body's main defenses against
bacteria. Neutrophils kill
bacteria by ingesting them. But the immune system can definitely get overwhelmed by bacteria and that can lead to a very serious condition called sepsis where the response to infection starts to damage organs. Infections leading to sepsis are usually bacterial but can be fungal or viral. Scientists are still trying to find cures and treatments for sepsis.
G. Holmes Braddock Senior High School, Florida: How does Radiation change the structure and function of a cell? Jacob Nordman: Radiation can come from many sources, and its effects are varied. Radiation ionization can cause breakage of chemical bonds or
oxidation (addition of oxygen atoms) of the affected molecules. The major effect in cells is DNA breaks. Since DNA consists of a pair of complementary double strands, breaks of either a single strand or both strands can occur. However, the latter is believed to be much more important biologically. Most single-strand breaks can be repaired normally thanks to the double-stranded nature of the DNA molecule (the two strands complement each other, so that an intact strand can serve as a template for repair of its damaged, opposite strand). In the case of double-strand breaks, however, repair is more difficult and erroneous rejoining of broken ends may occur. These breaks can profoundly affect cell function, leading to mutations, protein misfolding, or complete deletions of genes that can undermine the health of a cell, or even lead to its death.
Coppell Middle School North, Texas: About how many cells are in a human fingernail? Stefan Maas: Hello, Fingernails are composed of a protein (keratin). However, this hard, transparent material arises from layers of dead cells. So if you count dead cells, then there are thousands of cells that make up each fingernail.
Check your cell IQ!
Which of the following is not part of a bacterial cell?
We're ready to answer more of your questions. Keep them coming!
Marriotts Ridge, Maryland: If you break a bone in your body, are the cells that replace the ones you lost just as strong as the original cells?
Jacob Nordman: Hello Marriotts Ridge! The cells that replace the damaged ones when a bone is broken are not stronger or healthier than the original ones, and there is increasing evidence that neither are the bones, as was previously thought. While there may be a brief period in the healing process when the fracture site is stronger than the surrounding bone, they later reach equal strength, and the fracture site is no more or less likely to break again. The bottom line: healed bones and new cells are not stronger than they were before a fracture.
Souhegan High School, New Hampshire: Can one predict the person's lifespan based on the size of their telomeres? Kristine Willis: Hi, that's a really good question. Scientists are still studying how telomere length relates to lifespan; it's a complicated issue. Some of this research is done in mice. On one hand, we know that mice can live without telomerase, the protein that replicates a cell's telomeres; but on the other hand, mice without telomerase are more prone to genomic instability, and genomic instability can lead to problems like cancer and cell death. Maybe you'll become a scientist and discover the answer. ;)
Coppell Middle School North, Texas: What kind of effect does Leukemia have on cells? Stefan Maas: Leukemia is a type of cancer that affects blood cells (often the white blood cells). While this means that a large number of cells are being produced, they do usually not develop and function properly. There are many different types of leukemia. Some types of leukemia are more common in children, while others are more frequent in adults.
St. Stephen School, Connecticut: Can knowledge be transferred through DNA?
Amicia Elliott: Hi St. Stephen School! Thanks for the question. If we define knowledge as information, then definitely! DNA carries information in a number of ways: including coding specific sequences that become proteins, information about when to turn genes on and off via epigenetic markers, a variety of regulators like microRNA that also control cellular function. DNA is a highly dynamic storage system for information and we are still learning about how this information is transferred and what types of information there are. One thing that we are starting to appreciate is the role of epigenetic regulation in behavior.
Coppell Middle School North, Texas: How much energy does an animal cell make in a typical day? Can you tell me more about ATP?
Janna Wehrle: Hi! Hard to say generally. Some cells are so much bigger than others. Some work harder when the organism is active and running around. Others tool along at the same rate almost no matter what. They use VERY different amounts of ATP each day/minute/second. ATP is a chemical with two parts: the 'A' part is an organic chemical that carries the PPP energy part to different cell enzymes that need it. The three 'P' groups each represent a phosphate group. The Ps are connected to each other by high energy chemical bonds. When these bonds are broken in the right way, the energy can be used to drive other, energy-requiring reactions, like water falling down over a turbine in a dam.
St. Stephen School, Connecticut: Can knowledge be transferred from parent to child through DNA? Amicia Elliott: Hi St. Stephen School. Please check out the answer to a previous question about transferring information via DNA!
Colonia High School, New Jersey: What are the best and worst parts of your job as a cell biologist? Would you recommend it to others? Jessica Faupel-Badger: Thanks for this great question! I would say the best part is being able to ask questions about how cells work. Sometimes you get to ask a question in a new way, one that has never been asked before, and you learn something new. Then you need to let everyone else know about your discovery so they can build on this to learn even more about cell biology. The worst part is that learning something new can take a long time, so you need to have both patience and perseverance. I have the perseverance but the patience part is harder for me.
Clarkstown High School North, New York: How did the first cell come to be?Shiva Singh: Cells came into being from assembly of simple molecules over a long period of evolution.
St. Stephen School, Connecticut:What holds cells together, like what keeps skin cells from falling apart?
Stefan Maas: The cells within the different tissues of the body (including skin cells) secrete molecules into the environment that provide support for the surrounding cells and helps holding them together. This material between the cells is called the extracellular matrix (ECM).
St. Stephen School, Connecticut: If my parents are intelligent, will I be intelligent also? Does this involve DNA? Amicia Elliott: This is a great question! Heritability is the term used to describe how much variation in a trait, like intelligence, is related to genes (DNA). We can do specific types of studies to estimate how strongly related to genes intelligence is. Typically, it has been identified as highly heritable, suggesting that if your parents are intelligent, you are very likely to also be intelligent. However, recent studies are challenging this idea by varying the culture and environment that a child is raised in as well as the definition of intelligence. In any scientific study, the way that you define your variables makes a huge difference in the answers that you obtain from your experiments.
Colonia High School, New Jersey: How does aging affect cell division? Alison Gammie: Hi Colonia High School! Most scientists now agree that aging is, at least in part, the result of accumulating damage to molecules—such as proteins, lipids, and nucleic acids (DNA and RNA)—that make up our cells. If enough molecules are damaged, our cells will function less well and eventually stop dividing. In many respects, cells appear to age much like a car does: the parts start to wear out and gradually lose the ability to function.
Check your cell IQ!
What is apoptosis?
Marriotts Ridge, Maryland: Is there a specific disease that stops the growth of cells? How do these diseases work? Michael Bender: That is a great question. I would think that a mutation that completely stops growth would just cause death because many human cell types (like skin or gut or blood cells) turn over very rapidly and you couldn't do without them. There are many types of cell defects in disease -for example cells that are too large (hypertrophy), or cells that are too numerous (hyperplasia). Oftentimes these cell defects result from defects in hormones or other signals that help to coordinate cell growth during development.
Colonia High School, New Jersey: How did cells ever "figure out" how to create enzymes(as in how did the first cell make the first enzyme)?Susan Haynes: Hi. Evolutionary biologists have been trying to figure this out and the answer is still not completely known. In fact, the first enzymes are likely to have been made of RNA (not protein) and weren't part of cells as we know them today. This is known as the RNA world hypothesis, and there's a lot of evidence for it. The first enzymes would have been self-replicating RNA molecules, and those that were most successful at self-replicating survived.
St. Stephen School, Connecticut: Can cells be artificially produced in a lab?
Jacob Nordman: Greetings St. Stephens! Not only can cells be artificially produced in the lab, but they are a hallmark and critical piece in our understanding of how cells function. There are a number of cells that have been 'transformed' from existing cells found in the body, such as human embryonic kidney cells (HEK), pheocromocytoma cells type 12 (PC12), or neuroblastoma cell line 2a (N2a). HEK cells for example were changed by scientists in the 1970s to allow for foreign gene expression (transfection) and efficient production of proteins. Stem cells can be induced to transform into specific cell types in the lab through the use of various factors, and have been instrumental in designing therapies for many diseases. Finally, many variations for artificial cell preparation and encapsulation have been developed. Typically, vesicles such as a
liposome are synthesized. These can be used to mimic the functions of a cell. Great question!
Colonia High School, New Jersey: What does a typical day at work look like? Amicia Elliott: Hi Colonia High School, thanks for the question! The truth is that every day at work is an adventure. A typical day includes some of the following things: reading scientific papers, thinking about and designing experiments (my favorite part!), carrying out those experiments, data analysis and discussing results. A postdoctoral fellow works long hours to accomplish all of these things, but it is mostly a labor of love!
Colonia High School, New Jersey: How far do you believe science could progress if ethics and morality were not taken into account? OCPL Team19: That's an interesting question and should be directed to someone who works in the field of bioethics.
Jonas Clarke Middle School, Massachusetts: When and how was the very fist cell created?
Shiva Singh: Thanks for your question, Jonas Clarke Middle school. I recently answered a similar question, "Cells came into being from assembly of simple molecules over a long period of evolution."
Union High School, Oklahoma: If a human gets cloned, will the cells and DNA also be copied or could the cells or DNA be different?
Amicia Elliott: Hey there, Union High School. This is an interesting question! A clone, by definition, has the same starting cell and DNA makeup. However, a clone may go through development in a variety of different environments with different external stimuli, etc. This may have a profound effect on the cells and DNA in the adult. Check out Dolly the Sheep for some great information on cloning whole animals.
G. Holmes Braddock Senior High School, Florida: Are you more vulnerable to carcinogens in old age? Kristine Willis: Hi Braddock HS! That's a good question. We don't know everything about what makes people vulnerable to carcinogens, but genetics and environment both play a role. We think cancer is more common in older people because development of the disease is often (but not always!) slow. It can take time for cells to become cancerous and grow into a tumor after a person is exposed to a carcinogen; people of every age are vulnerable, but older people may get sick with other health problems before an exposure to a carcinogen results in cancer.
Jonas Clarke Middle School, Massachusetts: What is the one thing you would like to know about cells that scientists haven’t figured out yet?
Janna Wehrle: Thank. you! It's a fun question to think about. Maybe my personal BIG UNANSWERED QUESTION is how the proteins in the membrane around the outside of the cell change the shape of the cell when it needs to divide or grow. The membrane is made of oily molecules called lipids, but the proteins in the membrane can make the shape go from round and long and spindly. We are beginning to understand this--but we don't have the answer yet.
Union High School, Oklahoma: Why can't cells signal that they have a virus in them, and could there be a way to manipulate the cell so they can detect when a virus is inside of them? Stefan Maas: Hello, that is a great question! Generally, a cell does sense when it has been infected by a virus (for example by detecting the foreign viral genetic material) and it will usually elicit its defenses against it. Over the course of evolution the constant arms race between viruses and their host cells has generated defensive mechanism on the part of the host (such as molecules that prevent infection or weaken the virus once inside the cell) as well as the virus (such as counteracting any of the defensive molecules from the host, or in some cases taking over the cellular machinery of the host cells for the purpose of viral reproduction).
Colonia High School, New Jersey: Humans are able to receive organ transplants, is it possible for cells to go through the same thing if they have a defective organelle? Alison Gammie: Hello Colonia! Thanks for another great question. Yes, it is possible! There are some diseases resulting from defective mitochondria. Recently, scientists have found a way to remove the nucleus from an egg cell with healthy mitochondria and replace it with another nucleus from a person wanting to have a child. They do this so that a person with defective mitochondria is able to have a baby with healthy mitochondria. The scientists found out this technique worked better than trying to put healthy mitochondria into an egg cell. When you think about it, it makes sense because there are many mitochondria and only one nucleus.
St. Stephen School, Connecticut: Is there a way to see the scientists answering our questions? OCPL Team19: You can 'meet' our Cell Day scientists on the Cell Day website. We'll post pictures from the chat room on Twitter @NIGMS throughout the day. If you tweet about Cell Day, please use #CellDay2016!
Jonas Clarke Middle School, Massachusetts: If you could be any type of cell, what would you be and why?Jacob Nordman: Fascinating question, Jonas Clarke! Unequivocally I would be a neuron (brain cell). Neurons are the most super of the super computers found in the universe. They are incredibly specialized cells that perform jaw dropping computations faster than any computer and give rise to something no computer can accomplish, consciousness. Neurons gave up their ability to divide that other cells of the body have in order to form dense networks with other neurons and cells. This network is what produces sensory processing, deliberate motor tasks, emotion and thought. They also receive inputs from all over the body, allowing for an extremely integrated system. Neurons also have beautiful shapes:
http://fractalfoundation.org/OFCA/neuron2.jpg. Ultimately, the neuron is the democratic processing cell of the body, aware of itself and the body it is housed in, and responsible for protecting and sating it.
Colonia High School, New Jersey: How did your high school education prepare you for your job? Michael Bender: The most important thing was that it encouraged my interest in biology. My Indiana high school biology class had a great marine biology unit, where we spent a week in the Florida keys snorkeling and collecting and classifying marine invertebrates. It made me think I might want a career as a marine biologist. (Thanks Coach Weaver!) In college, I became more interested in genetics and ultimately made my career in that area.
Jonas Clarke Middle School, Massachusetts: What are some new exciting discoveries that have been made about cells recently? Jessica Faupel-Badger: Hi Jonas Clarke Middle School! Cell biology is a very broad field, and each person in the room might have a different answer to this question based on their own interests. A great place to learn about recent advances in cell biology is the NIGMS Biomedical Beat blog -
https://biobeat.nigms.nih.gov/. One function of the cell that you may not be aware of is autophagy, the process of the cell recycling and degrading intracellular components. Autophagy was the subject of the 2016 Nobel Prize in Physiology or Medicine -
Arkadelphia High School, Arkansas: What are the most common errors in mitosis that lead to cancer?Kristine Willis: Hi AHS Biology! Good question. There's no one mitotic error that most commonly leads to cancer; there are lots of different mutations. You can classify them into a few common categories, though. Cells can partition their chromosomes unevenly when a mother divides into two daughters, leading to chromosome loss (aneuploidy) or extra chromosomes (polyploidy); double stranded breaks in DNA can be improperly repaired, resulting in chromosomal translocations (for an example, check out the story of the famous Philadelphia chromosome, which was described by Janet Rowley:
https://en.wikipedia.org/wiki/Philadelphia_chromosome; or single point mutations can arise, for example as a result of errors made by the cell when it replicates its DNA.
Hello students! We are ready for your questions.
Union High School, Oklahoma: What do you consider this industry's biggest challenge now and in the future? Susan Haynes: Hi, Do you mean biomedical research in general? While scientific research has answered many questions, still more remain, which is what makes it so exciting! We still need to understand more about how cells and tissues function normally, and what goes wrong in disease. And translating this knowledge into effective therapies is always a challenge - human biology is complicated and it takes a lot of research to make sure that new therapies don't cause other problems. And finally, we always need people interested in doing scientific research. So if this really interests you, consider a career in science!
Marriotts Ridge, Maryland: How many years of college did you have to complete to get the position you're at right now? And is it difficult (but not impossible) to complete your studies at your college? Amicia Elliott: Hi there Marriotts Ridge, thanks for the question! I completed 4 years of B.S. and 4.5 years of Ph.D. for the position that I'm in right now. It was a challenging road, but definitely not impossible and it has been super rewarding!
Union High School, Oklahoma: How do cells know what to do? Like what does one cell by itself do besides sit there? I don't understand how a bunch of little spheres make up my whole being and function. Do they contract and relax like a smaller version of a muscle? Shireen Sarraf: That's a complicated question! The ultimate control of the cell comes from the nucleus, where the DNA is stored. The DNA contains information that tells the cell what proteins to make and when to activate them. Cells release proteins into their environment that act as scaffolds then use these proteins as well as chemicals to communicate with each other and this is how they can act together to form tissues and organs. As an organism develops, different genes in the nucleus (DNA) are active, therefore different proteins are made, and the cell can function as part of the organism.
Union High School, Oklahoma: What happens if a cell's mitochondria are destroyed? Jessica Faupel-Badger:The mitochondria are the cell's power house - producing energy in the form of ATP. Without this vital function, the cells would die. However, there are examples of cells that do not have mitochondria. Prokaryotic cells do not have mitochondria. There are also numerous human diseases that are associated with mitochondria that are not functioning properly.
Marriotts Ridge, Maryland: Are there any organelles that a cell can live without? Stefan Maas: Well; some organelles exist in multiple copies in each cell (such as mitochondria), so some of those copies could be lost without much of an impact. However, for the normal functioning of the cell and long-term survival the cell can't lose all of the mitochondria. The nucleus is a type of organelle of which there is only one per cell. Some highly specialized cells (red blood cells) lose their nucleus during their maturation. But again, in order for a cell to be able to survive and divide, the nucleus is essential.
Union High School, Oklahoma: How are cancer-fighting properties in white and green tea or camellia flowers determined? Is there a way to amplify these properties to help fight cancer? Shiva Singh: Scientists usually start this process by conducting experiments on the cancer-fighting (and other beneficial properties) of natural or human-made compounds in cell culture in plastic dishes, and then move up the experimentation to small animals like mice. When scientists determine that the product potentially has anti-carcinogenic properties, they usually try to isolate (extract) and purify the active ingredient responsible for the beneficial property, and continue further experimentation in animals, and in some cases conduct clinical trials in humans. The isolated chemical may be combined with other chemicals to stabilize and enhance its properties. Scientists may also try to figure out the precise chemical structure of the isolated compound and then try to chemically synthesize it for better formulation.
Silva Health Magnet High School, Texas: How far away are we from creating synthetic cells and using them in living organisms? Darren Sledjeski: Hi! Nice question. The answer depends a bit on what you mean by "synthetic". Scientists have built a bacterial cell from scratch using known DNA (http://www.nature.com/news/minimal-cell-raises-stakes-in-race-to-harness-synthetic-life-1.19633). I wouldn't say it is synthetic, but it is still an amazing piece of work. My guess is we are still many years away from a truly synthetic cell. This is mostly because we still don't know what many of the genes do in the minimal cell described above. Until we know the purpose of all of the parts, it will be hard to build a synthetic cell.
Germantown Friends High School, Pennsylvania: How does one synthesize a cell? I've heard it was done recently.
Darren Sledjeski: Hi and thanks for the question. Currently, scientists create a synthetic cell by replacing the DNA in a living cell with DNA synthesized in the lab. My feeling it is really more of a cyborg cell than a truly synthetic cell. Maybe someone from your class will be the first one to make a synthetic cell.
Magoffin County High school, Kentucky: After the process of translation, how does the cell regulate the transport of these proteins to the desired location within the cell or excretion from the cell? Susan Haynes: Hi, This is a great question - protein targeting is very important for normal cell function. There are targeting signals embedded in the protein sequence or structure, or are created when proteins are modified after translation. For example, most transmembrane proteins or those that are secreted from the cell are directed to the right place (embedded in the membrane or directed to secretory vesicles) as part of the translation process itself (via the signal sequence at the beginning of the protein). Others, like proteins that are part of mitochondria, are released into the cytoplasm and then taken up by mitochondria. These proteins have targeting sequences that are recognized by receptors in the outer membrane of the mitochondria.
St. Charles School, New Mexico: Does a cell's nucleus change over time? Shireen Sarraf: Yes. One way this occurs is as an organism develops, matures or ages and it requires different things, for example: a baby versus a pregnant woman. In this case, the nucleus turns on genes that will produce proteins that allow cells to carry out the processes they need. Therefore, if you looked at which genes were expressed in a baby or a grown woman, you would see two different lists.
A second way the nucleus changes over time is when the DNA actually becomes chemically modified. This is called epigenetics. Exposure to different environments, such as smoking, can actually cause chemical groups to attach to the DNA and can affect the expression of genes. These changes don't actually change the DNA code, but can affect the way the code works.
Silva Health Magnet High School, Texas: According to your experience, what has been the most difficult experiment or research that you've done?Paula Flicker: Working with botulinum toxin, the protein that causes botulism, was difficult because it is very dangerous. A very small amount is enough to kill 50 mice. I was careful to keep the samples locked away when not working with them and sterilized glassware that had been in contact with the sample.
Greenhill School, Texas: If a new type of cell was discovered, how would it be named and classified?
Darren Sledjeski: Hi Greenhill! We are discovering new types of bacterial cells all of the time. The current process involves sequencing its DNA and comparing it to all other bacteria whose DNA has been sequenced. Then we figure out which known bacteria it is most closely related to. If it is different enough, (and that cutoff is a bit arbitrary) it gets a new name picked by the discoverer. So, it is very possible that one day, if you become a scientist, you could name new bacteria after your friends or family. If you want to explore the tree of life, check out this
St. Charles School, New Mexico: What happens if an organelle is missing in a cell? Tracy Koretsky: Most organelles are essential so if a cell loses an organelle during growth or division, the cell will in most cases die. Some bacteria and yeast cells can live without mitochondria and use anaerobic respiration for growth.
Coppell Middle School North, Texas: I was looking at animal cells through a microscope and saw a bunch of cells and I noticed that some were bigger than others. Does that mean they have to work harder?
Paula Flicker: The components of a bigger cell may be bigger, e.g. nucleus, or more of them, e.g. ribosomes, such that per unit volume, the bigger cell may not be working harder. Different cell types may be working harder at different times.
Coppell Middle School North, Texas: Is there cytoplasm inside the nucleus? What would happen to your body if the cytoplasm disappeared? Amanda Melillo: Thanks for the question! Cytoplasm is the fluid that fills a cell. Similar to the cytoplasm of a cell, the nucleus contains 'nucleoplasm.' Nucleoplasm has a little different composition than the cytoplasm. Nucleoplasm can only be found inside of the nucleus. The nucleoplasm is the suspension fluid that holds the cell's chromatin and nucleolus.
The cytoplasm does more than just suspend the organelles. It uses its dissolved enzymes to break down all of those larger molecules, so the short answer to your second question is no.
Silva Health Magnet High School, Texas: How viable do you see the use of artificial prosthetic tissue in damaged cells?Donna Krasnewich: This is an interesting question, I am guessing that you are curious about growing artificial organs (prosthetic tissue) and using them to helping people who have a diseased organ. These artificial organs can be used to supplement function in some people or support others as they are awaiting a transplant or even allow others to avoid a transplant. There is active research going on in heart tissue, lung tissue, liver tissue and others. Artificial organs are very complex problems, as you can imagine, since they not only have to perform the function but they have to do it at the right time and at the right rate for the entire body, responding to the correct cues from the rest of the organs. I hope that your curious nature brings you into science so you can help solve these important problems.
St. Charles School, New Mexico: How are cells so powerful, since they are so small? Alison Cole: That's a very interesting question and there are lots of ways to answer it. One way is to say that even though they are tiny, cells still have the ability to grow and reproduce, and that is due to the presence of DNA, the hereditary material of genes, and RNA, containing the information necessary to build various proteins such as enzymes, the cell's primary machinery. All cells (except red blood cells which lack a cell nucleus and most organelles to accommodate maximum space for hemoglobin) possess this hereditary material. It's amazing that so much genetic material can fit into these tiny cells!
Germantown Friends High School, Pennsylvania: What are the biggest and smallest cells?
OCPL Team19: Bacteria are certainly the smallest, and an ostrich egg is the largest, but in humans, the largest cell in diameter (across) is the egg cell. Some of the longest cells in the body are nerve cells--they can be over 3 feet long.
Here are some very small human cells:Sperm – diameter of 1-3micrometers, but its tail is 50 micrometers.
Cerebellum granule cells, which are key to the sense of smell – diameter of 4-10 micrometers.The red blood cell –diameter of 4-8 micrometers.
Greenhill School, Texas: What is the largest cell overall? OCPL Team19: An ostrich cell!
St. Charles School, New Mexico: Are there cell functions that require multiple cells to occur?
Darren Sledjeski: Hi St. Charles. The simple answer is YES! In multicellular organisms, like humans, culardifferent cells work together to, for instance, fight infection or produce red blood cells. Even bacteria can work as a team to survive in environments that they could not live in independently. Bacteria X consumes a nutrient and produces a waste product that is toxic to it but is a nutrient for bacteria Y. Therefore the bacteria need each other to survive.
St. Charles School, New Mexico: Why do DNA and RNA only occur in certain parts of eukaryotic cells? How does this benefit the cell?Tracy Koretsky: As you may already know, most DNA in cells remains in the nucleus except for the DNA of the mitochondria. The DNA in the nucleus is copied into RNA, and the RNA is transported from the nucleus to cytoplasm for translation into proteins. It is beneficial for the DNA to be protected in the nucleus b/c it is the master copy.
Union High School, Oklahoma: Is it possible to synthesize chromosomes? If so, is it possible to cure down syndrome with this technique? Kristine Willis: Hi! Wow, that's a hard one, but a good one. Let's take it in two parts. First, is it possible to synthesize chromosomes? We can pretty easily synthesize long molecules of DNA but chromosomes are harder, because they are made up not only of DNA, but also lots of different proteins and chemical modifications (like methylation). Getting all those parts assembled correctly, *exactly* the way they are in a cell, isn't straightforward. Down's Syndrome is actually caused by having a third copy of chromosome 21 (normally there are only two copies), so from a purely theoretical standpoint, a synthetic chromosome wouldn't be a cure. Practically, we're many years away from being able to use synthetic chromosomes in medicine. If you're interested in synthetic biology, maybe you'll all become scientists and help us learn more!
St. Charles School, New Mexico: How do cells age while you are aging? Joe Gindhart: That is a great question. How cells age depends in part on what kind of cell we are studying. Cells that divide often run the risk of having shorter telomeres at the end of chromosomes; telomeres act as 'insulation' that protects the genes near chromosome ends from deletion. Cell death can be triggered when telomeres become too short. Mutations can accumulate in cells that divide rapidly, which can affect protein function or gene regulation essential for normal cell function. Long-lived cells such as neurons can accumulate damaged proteins that can disrupt cell function and eventually cause cell death. Thanks for your interest in Cell Day!
Union High School, Oklahoma: What are the most common jobs for college graduates with degrees in biology, molecular biology or cellular biology? Krishan Arora: Good Question! College graduates with degrees in biology, molecular biology, or cellular biology can work as research scientist/technician in a research laboratory at an academic institution or a biotech company. They can be science writers. They can be problem solvers to provide solutions to the complex issues in the area of biomedical sciences.
Germantown Friends High School, Pennsylvania: How does muscle tissue enlarge itself? For example, an athlete will get bigger and stronger from working out. What happens to our muscle tissue when this happens?
OCPL Team19: Skeletal muscles grow when the cells within them grow in size and number. There's a good description of the process at
Germantown Friends High School, Pennsylvania: What is the difference between plant and an animal cell? Susan Haynes: Plant and animal cells differ in a number of ways, but it's important to remember that there are more similarities than differences! In terms of differences, plants have cell walls to give them a fixed shape and protect them from injury. But animal cells do not have cell walls, and instead use an internal cytoskeletal system to maintain their shape and cushion them against any external injuries. This cytoskeletal system can be flexible, allowing some animal cells to change their shapes. Another significant difference is that most plant cells use photosynthesis (using the energy from sunlight to make sugar molecules), and animal cells do not. They have to take in nutrients from the environment to make energy and synthesize molecules.
Germantown Friends High School, Pennsylvania: Good morning! How fast do cells multiply?
Shireen Sarraf: Good morning! There are many different kinds of cells in the body which therefore have many different properties. Some cells, like epithelial cells, which make up your skin and gut lining, divide quickly - every day. This makes sense because your skin is constantly exposed to damage from the environment and needs to be replaced. Other cells, like many types of neurons, do not divide once they become mature. Therefore, if that neuron becomes damaged, it will not be replaced. This is the basis of some neurodegenerative disorders, like Parkinson's disease, where neurons that control movement die and are not replaced. In cancer, cells lose control of their growth rate (which is usually very regulated) and multiply abnormally. This leads to tumor growth. Bacterial cells on the other hand, which are much simpler, multiply very quickly, some in 15-20 minutes. This explains why a bacterial infection can overwhelm you so fast.
St. Charles School, New Mexico: Are there times when plant cells do NOT perform photosynthesis in sunlight? How do the cells know when to perform photosynthesis?
Darren Sledjeski: Hello again St. Charles. Photosynthesis is dependent on sunlight. If sunlight is available then plants will use it to produce glucose. Plants do have ways of detecting if sufficient sunlight is available for photosynthesis. They use pigments like cholorphyll or beta-carotene to detect sunlight.
Mountlake Terrace High School, Washington: How do neurons "fire off" in the brain? And how does this result in thoughts? OCPL Team19: Excellent question, and maybe you'll be the one to provide the complete answer! Right now, scientists know that nerve cells conduct electrical charges that speed down their length and spread to connecting nerve cells. Scientists also know that some nerves squirt out certain chemicals, like acetylcholine, serotonin and dopamine, that have specific effects in the body. But no one really understands how these electrical and chemical reactions result in thoughts. If you learn the answer, please let us know!!
St. Charles School, New Mexico: Can specialized cells ever change jobs? Donna Krasnewich: What an interesting question! It turns out that many specialized cells, like heart muscle cells or neurons in your brain work very hard and use lots of energy to become highly specialized. These types of cells probably don't switch jobs in the body. However, let's think about cells in the immune system. Their job include protecting us from invading viruses and bacteria. They have to change a lot, since the virus or bacteria may be new to them, they have never seen it before so they have to be ready to change to recognize this new 'invader' and kill it off. Their ultimate function is the same but they have to be able to distinguish between their own cells and 'invading' cells. The other example is stem cells, these are cells that have the capacity to become many different kinds of cells in the body. There is a lot of research on how stem cells become more specialized cells, this has exciting potential to treat disease and improve health.
Greenhill School, Texas: When a cell dies, what happens to the remains?
Tracy Koretsky: If this is a bacteria or a yeast, the cell simply degrades and the contents are released into the environment. If you are a complex multicellular organism with an immune system, the dead cells will be subject to phagocytosis by macrophages and cleared from the body.
G. Holmes Braddock Senior High School, Florida: Could the DNA of a lizard with regenerative abilities be fused with human stem cells to regrow lost limbs?
Joe Gindhart: Wow, that is an awesome question. Scientists have been fascinated by limb regeneration in lizards and amphibians for a long time. This field of study is relevant to human disease because it would be great if we could regrow a lost finger or hand, but imagine if someone with a diseased organ like a heart or lung could grow a new replacement organ. Are there genes in lizards that could be engineered into human cells to allow regeneration? That would be a great experiment. However, my hypothesis is that transplanting all of a lizard's DNA into human stem cells would not work, because the lizard genes required for 'lizardness' would interfere with normal human development.
A movable skeleton Like a hospital X-ray photo showing a person’s bony skeleton, this image reveals the structure of a cell’s skeleton. The cell is a human skin cell, and its skeleton (more formally called the cytoskeleton) shows up as a network of thin strings and threads. Unlike bony skeletons, which retain the same basic shape throughout our lives, cytoskeletons are constantly changing, allowing cells to grow and move. Learn more about this image and the researcher behind it, Torsten Wittmann, at the University of California, San Francisco, in the NIH director’s blog post at
Greenhill School, Texas: How often do you find a different type of cell?
Darren Sledjeski: Hi Texas! Scientists who study bacteria and fungi are finding new cells every day. It is estimated that we have discovered only a small fraction of the types of free living cells that exist. In our own bodies, scientists regularly find different types of cells, but all of these cells share the same DNA.
Germantown Friends High School, Pennsylvania: What disease damages cells the most?Amanda Melillo: Hi PhillyFriends! Thank you for your question! By definition, disease itself is an abnormal condition that damages an organism. Damage can affect many different parts of the cell, for example, the DNA. DNA damage to a cell can lead to disease such as cancer. Various infectious disease can also cause lots of damage to cells, however, our immune systems have the ability to fight back against the infection and help to repair damage. In certain cases, our immune systems itself could also lead to damage to our cells, which are called autoimmune disease.
Thanks for joining us! We look forward to answering your questions. Keep them coming...
Greenhill School, Texas: What happens if the cell membrane breaks open and does not fix? Paula Flicker: Cell death processes would start breaking down the cellular components. Products of cell death may be released into the extracellular space.
G. Holmes Braddock Senior High School, Florida: How does aging occur in cells? Can we delay it?
Shireen Sarraf: Welcome to Cell Day! Research has shown that most cells and therefore organisms have a defined life span as cells eventually lose the ability to reproduce and replenish themselves. Many scientists are working towards understanding the genes that are involved in aging and environmental factors that affect how these genes are expressed. One specific change that occurs is at the end of each chromosome, where there are structures called telomeres. Telomeres are DNA-protein structures that protect the chromosome ends; when telomeres have reached a critical length after numerous cell divisions, the DNA ends can no longer be properly replicated. Because shortened telomeres are dysfunctional, repair cannot occur, the cell can't divide and the cell has reached the end of its replicative life.
Take a look at these links for more information: https://www.nia.nih.gov/health/publication/can-we-prevent-aging,
Arkadelphia High School, Arkansas: Would you theorize being able to control or modify the mitosis of a cell could be an end to cancerous cells? Tracy Koretsky: Yes, most cancerous cells have escaped normal growth regulation. If we could specifically target the quick growing diseased cells and stop mitosis, we could bring an end to cancer.
Birth of a yeast cell Yeast make bread, beer and wine. And like us, yeast can reproduce sexually. A mother and father cell fuse and create one large cell that contains four offspring. When environmental conditions are favorable, the offspring are released, as shown here. Yeast are also a popular study subject for scientists. Research on yeast has yielded vast knowledge about basic cellular and molecular biology as well as about myriad human diseases, including colon cancer and various metabolic disorders. To download a high-resolution version of this image, go to
Check your cell IQ!
Which of the following is not involved in cell movement?
Union High School, Oklahoma: Is there a way to create cells and if so do you ever think it will be possible to make working body parts (like a heart) out of them? Darren Sledjeski: Hi Tulsa! Yes, we can engineer cells to change how they function. Recently scientists have developed new methods based on a Protein:RNA system called CRISPR-CAS9 that makes it even easier. Other scientists are working on 'building' organs from scratch in the lab. In fact, some scientists have synthesized 'meat' in the lab too. I don't know when these different technologies will come together to build a heart, but we are on our way. Maybe someone from your school will be the first one to do it.
Union High School, Oklahoma: How do stem cells become other cells (differentiate)?
Paula Flicker: Stem cells become other cells by expressing only certain genes. For example, a muscle cell will be generated by producing large numbers of the proteins that generate a muscle fibril such as myosin and actin.
G. Holmes Braddock Senior High School, Florida: Have people in Africa started evolving resistance to AIDS? Donna Krasnewich: Wow, this question stimulated a lot of discussion in the room! Evolution happens in humans over long periods of time, many thousands of years, and HIV infection is relatively newly recognized in the world, the first cases were reported 40 years ago. So, there has not been enough time to evolve a new mechanism to resist HIV infection. HIV infection and AIDS, the resulting clinical problems, is still a very serious problem in Africa. There are some children and adults who do not get symptoms after infection with HIV. They are being studied so that physician-scientists can understand how their body protects them from HIV infection.
Union High School, Oklahoma: What cell divides the slowest? Krishan Arora: Great question! In the human body, the slowest dividing cells are the nerve cells. There are also certain bacteria in the Antarctica that do not divide for decades.
Union High School, Oklahoma: What is the rate of cells dying compared to the rate of cells dividing? Tracy Koretsky: Good question. I can't really give you a numerical answer. Many cells in the body are constantly turning over. Cells of the small intestine only survive 2-4 days. Skin cells turn over every 10-30 days. Nerve cells stop dividing when fully differentiated. So some cells are constantly dying and new cells are created by cell division whereas other cells are not replaced after they die.
Davies Career & Technical High School, Rhode Island: What are some of the causes for normal cells to become cancerous? Shireen Sarraf: Hello Davies High School! Cancer has many different causes. Through many different mechanisms, the DNA of normal cells can accumulate mutations over time. Some cancers are strongly associated with viral infections (e.g. hepatitis B and C viruses, human papillomavirus), others are strongly associated with lifestyle factors (e.g. smoking and alcohol use), so there are known strategies for preventing certain types of cancer. However, many mutations to the DNA arise from our own processes inside our body that by chance accidentally led to the mutations occurring. These mutations can then be passed on to daughter cells during mitosis. With successive rounds of cell division, more mutations can accumulate eventually transforming a normal cell into a cancer cell. This process can take decades, which is why cancer is more often seen in older individuals. Our current understanding of cancer arising from our own genes led to two scientists from the United States receiving the Nobel Prize in 1989!
Seaman High School, Kansas: Who first came up with the theory of endosymbiosis? Like who first thought of it? How was the theory supported by others? Joe Gindhart: The theory of endosymbiosis as a model for the evolution of eukaryotic cells from prokaryotes was first proposed in the early 1900s, but experimental evidence supporting the theory was first reported by Lynn Margulis and colleagues in the 1960s. With the advent of DNA sequencing, we can see that organelles such as mitochondria and chloroplasts have genes related to bacteria. The Wikipedia page for endosymbiosis (https://en.wikipedia.org/wiki/Symbiogenesis) has a more detailed explanation. Thanks for your question and for your support of Cell Day!
Check your cell IQ! The largest human cell (by volume) is the egg.
Davies Career & Technical High School, Rhode Island: Is it possible to take a fully mature lung cell from my body and "grow" it into a complete lung?Darren Sledjeski: Hi DCTHS! Not yet. Scientists are working hard on changing mature, differentiated cells into pluripotent stem cells that could then be used to grow a complete lung. But, you need more than just the cells. You need a scaffold for the cells to grow on that will have them form a lung. Many groups of scientists are working on different parts of this problem. They have gotten far enough to make a
Hey Chestnut Ridge Lions! Glad to see you participating. Your question is being answered. Stay tuned!
Davies Career & Technical High School, Rhode Island: Do cancer cells of all types (stomach, breast, colon, etc) have the same functions/goals? Donna Krasnewich: The characteristic that all cancer cells have in common is that they have uninhibited replication rates, they continue to grow and replicate when they should stop. This is the same for all types of cancer cells, including stomach, breast cancer cells. Remember, there are cancer cells in solid tumors, like breast and liver tumors, and also cancer cells that are in the blood, like leukemia, where blood cell numbers increase astronomically. The other thing that cancer cells can do is metastasize. This means that cells from the original tumor break off and settle into other organs and continue to replicate and grow causing new problems. There is a lot of research into how cancer cells work and how to stop them. Thanks for asking this interesting question.
Chestnut Ridge High School, Pennsylvania: What happens when cells die? Where do the leftover part go? How is it cleaned up?
Tracy Koretsky: In multicellular organisms with immune systems, dead cells are cleared from the body by macrophages via phagocytosis. The cellular remains are degraded in the lysosome.
St. Charles School, New Mexico: What is the biggest cell in the human body? Moderator Team: The largest human cell in diameter (across) is the egg cell, which can just barely be seen with the naked eye. Some of the longest cells in the body are nerve cells. Some nerve cells in your spine can be over 3 feet long as they send their projections from your spine all the way down to your toes.
Davies Career & Technical High School, Rhode Island: Polycystic kidney disease runs in my family. If I express the gene for this, does that mean I will develop kidney disease? Joe Gindhart: Thank you for your question. Many types of polycystic kidney disease have a genetic origin, and the functions of proteins involved in kidney development and cilia activity are the subject of intense research. The genetic concepts of penetrance and expressivity are important to keep in mind. Penetrance is the percentage of individuals carrying a trait that display the trait, and expressivity is the 'strength' of a trait in an individual. This is a complicated way of saying that carrying the gene for a disease is only part of the story of whether the symptoms of a disease will occur. Thank you again for your question.
Jonas Clarke Middle School, Massachusetts:Which organelle does the most moving inside of a cell? Is there a way to measure how fast this organelle moves? ~Mira Menon
Shireen Sarraf: Hi! Great question. The inside of the cell is a very dynamic environment. Proteins and biochemical signal molecules need to move all over the cell in order to do their jobs. These proteins and molecules are often delivered by vesicles, which are membrane bound organelles that often originate at the Golgi apparatus and then travel through the cell to particular locations. In some cases, the cellular products are released/secreted outside the cell across its plasma membrane. This phenomenon has key role in synaptic neurotransmission, endocrine secretion, mucous secretion, etc. Scientists can measure vesicle movement by using microscopes to track vesicles labeled with fluorescent dyes.
Take a look at this link to see how crowded and dynamic the inside of a cell is:
Thanks for being patient with us. You'll see your questions and answers here shortly.
Seaman High School, Kansas: On a cellular level, what happens when you sprain a body part such as an ankle or a wrist?Donna Krasnewich: Remember the structure of joints; two bones at the joint are held together by connective tissue and tendons. Tendons are strong long cords, that are not stretchy. When you sprain a joint, typically you are stretching these tendons that hold the joint in place. When a sprain happens inflammation occurs, inflammations is the body's way to signal that there is damage and call in the 'repair team'. The damage to the tendon calls in immune cells (white blood cells) in waves, some signal more cells, some clear the damaged tissue (macrophages), others signal to stop the bleeding and still others repair the damage with the deposition of fibrous tissue (like scars). The swelling you see in a sprained joint is because all of these cells and blood flow coming into the joint lead to leaky small blood vessels (capillaries) and fluid flux into the joint area. After the damage is repaired the swelling from fluid and scar tissue goes down.
Check your cell IQ!
During the S phase of the cell cycle
King School, Connecticut: What is a cell?Joe Gindhart: That is a deep question! In a biological context, a cell is the smallest unit of life. As Rudolf Virchow wrote, 'Omnis cellula e cellula', which means all cells come from pre-existing cells. Cells were first observed in the 1600s by Robert Hooke, who used an early microscope to see the cell walls of plant tissue. Other scientists used better microscopes to see cells in pond water and see cells in every organism that was studied. In the 1830's, Schleiden and Schwann used these observations to formulate the cell theory. A little trivia: The name 'cell' was coined by Robert Hooke because of their resemblance to the rooms inhabited by monks in the Middle Ages. Thanks for your interest in Cell Day.
Your eye contains at least 70 different types of cells Each shade of color in this image—blue, green, purple or pink—represents a different layer of cells in the cross section of an eyeball. At least 70 different cell types work together to transform light into sight. Two scientists from the University of Utah used chemistry, computers and artistry to produce this remarkable image. Learn more in the NIH director’s blog post at
To see another image of the many cell types in the eye—including cones that allow us to see color and rods that help us see under low-light conditions—go to
http://www.nigms.nih.gov/education/life-magnified/Pages/9_bottom_eye_nerve_cell.aspx. High resolution versions of both images are freely available for download from the Life: Magnified collection http://www.nigms.nih.gov/education/life-magnified/pages/default.aspx.
St. Stephen School, Connecticut: Why do plant cells have a cell wall and animal cell do not?Tracy Koretsky: The cell wall of plant cells is a supportive structure so that the cells have a fixed shape and are protected from injury. Animal cells do no need to keep a rigid structure because they have a skeleton to protect the cells of their tissues and organs.
Magoffin County High School, Kentucky: How did the evolution of Eukaryotic cells lead to the diversifying of plant and animal cells? Darren Sledjeski: Hi Magoffin County HS! That is a great question. It is also a very difficult one to answer. We do not have a fossil record of the earliest eukaryotic cells so it is hard to follow their evolution. But, what we think is that once eukaryotic cells did evolve they provided a huge amount of flexibility for life to adapt to and evolve into the plants and animals we see today.
St. Stephen School, Connecticut: Do the ridges of fingerprints have specialized cell different from other body cells? Shireen Sarraf: Hi St. Stephen School! That's an interesting question. Your skin is composed of epithelial cells that are specialized to allow your fingertips to be extremely sensitive sensory organs. The ridges of your fingerprint are called 'friction ridges' which are formed by the underlying interface between the dermis and the epidermis, different layers of your skin. These ridges serve to amplify vibrations triggered when fingertips brush across an uneven surface which can then transmit the signals to sensory nerves. Fingerprint ridges also allow you to grip surfaces. Within the ridges of your fingerprints, there are sensory cells distributed over the surface in a very sophisticated design that allows you to detect pressure, pain, temperature and texture. These extremely sensitive and precise characteristics allow blind people to read Braille.
St. Stephen School, Connecticut: What is your opinion on the Endosymbiosis theory?Joe Gindhart: Good afternoon! The Science Kid asked a very similar question a few minutes ago. I think the endosymbiosis theory is legitimate, as there are clear similarities between plastid (mitochondria, chloroplasts, etc.) genomes and the genomes of certain bacteria. There is also evidence of gene transfer between the nuclear genome of the 'host' cell and the plastid genome of the endosymbiont. I used to wonder whether mitochondria or chloroplasts could live independently like bacteria, but they cannot because plastid genomes have lost many of the genes required for survival outside of the host cytoplasm. Thanks for your support of Cell Day.
Magoffin County High School, Kentucky: Could you explain the evolution of eukaryotic cells from primitive prokaryotic cells?Paula Flicker: It is not clear that eukaryotic cells evolved from prokaryotic cells. It is a hotly debated question. One current theory is that both prokaryotic and eukaryotic cells evolved from the same common ancestor.
St. Charles School, New Mexico: How does multiple myeloma damage the human body?Krishan Arora: Very Interesting question! In addition to pain and stress, there are many ways multiple myeloma affects human body, but it affects three main systems, blood, the kidneys and bones.
For example, number of myeloma cells can interfere with the production of all types of blood cells. A reduction in the number of white blood cells can increase the risk of infection, whereas decreased red blood cell production can result in anemia. A reduction in platelets can prevent normal blood clotting. In addition, high levels of a protein called M protein, and light chains of antibodies (also known as Bence Hones proteins), mess up normal functioning of immunoglobulins and cause the blood to “thicken.” Excess M protein in the blood can overwork the kidneys as they filter blood. The amount of urine produced can increase, and the kidneys fail to function normally.
Myeloma cell damage leads to bone loss as well. Bone destruction can cause the level of calcium in the bloodstream to rise, a condition called hypercalcemia, which can be a serious problem if appropriate treatment is not given immediately.
King School, Connecticut: How does lysosomal storage disease affect your body? Or when does it start to?Donna Krasnewich: Lysosomal storage diseases (LSD) are a group of disorders caused by rare genetic changes that lead to the inability of cells to break down complex sugar structures. These complex sugar structures have many functions in the cells, and as is true with many things in the cell, they are broken down and rebuilt as part of a natural cycle. A child or adult with a LSD cannot break down these complex sugar structures, called oligosaccharides, then they are stored in the cell, in the organelle called the lysosome. The lysosome becomes very bloated and often the cell dies and the storage material stays in place. In a person with an LSD, the storage may begin in infancy, but the symptoms may not appear until early childhood. Some LSDs show up in the teen years or even adulthood. Symptoms may be problems with development, unusually enlarging liver and spleen, bone problems and rounder faces when the storage is under the skin. Remember, these are very rare genetic disorders and physician-scientists are working to find ways to help children and adults with these disorders.
Magoffin County High School, Kentucky: What allows stem cells the ability to transform into specialized human cells?
Amanda Melillo: Hi MCHS Anatomy! Great question! Stem cells have the remarkable potential to develop into many different cell types in the body during early life and growth. When a stem cell divides, each new cell has the potential either to remain a stem cell or become another type of cell with a more specialized function, such as a muscle cell, a red blood cell or a brain cell. When unspecialized stem cells give rise to specialized cells, the process is called differentiation. While differentiating, the cell usually goes through several stages, becoming more specialized at each step. Scientists are just beginning to understand the signals inside and outside cells that trigger each step of the differentiation process. The interaction of signals during differentiation causes the cell's DNA to acquire epigenetic marks that restrict DNA expression in the cell and can be passed on through cell division.You can find more information on stem cells here -
Greenhill School, Texas: How are cancer cells formed differently than regular cells? Tracy Koretsky: In general, cancer cells are regular cells that have escaped the normal growth regulation process. Old cells do not die and growth is not controlled, producing a tumor. There are many ways that a cell can become cancerous, like exposure to chemicals or genetic mutations. Scientists are still learning all the different ways cancer cells can escape normal growth mechanisms.
Magoffin County High School, Kentucky: What differentiates the rate of progression in cancers of the same type in different people? Donna Krasnewich: This is a great question and leads to one of the most interesting concepts scientists are thinking about today. Why are each of us different? Remember that cancer is caused by a change in the genes in the DNA. Not all cancer cells have the same genetic changes, this means that the characteristics and aggressiveness of the cells may be different. AND each person is different, not just in the way they look and act but also in the way their body responds to disease. So some people may have more ability to respond to cancer and kill off cancer cells, while others have immune cells that do not recognize the cancer cells are bad so they do not mount an attack. Together, the differences in cancer cells and variation in people's ability to recognize cancers would lead to different rates of cancer progression.
Mountlake Terrace High School, Washington: In a cat how many different types of cells are their?Paula Flicker: Cats have a similar number of different types of cells as humans. The number of different cells in humans is estimated to be about 200. A given type of cell might be different in number or size in cats versus humans.
Arkadelphia High School, Arkansas: Is there a way to make a vaccine for cancer using a method similar to the flu shot?Darren Sledjeski: Hi Arkadelphia! Sweet question. Many scientists are working on that exact problem. The HPV vaccine is an anti-cancer vaccine. And others are in development. The National Cancer Institute (part of the NIH) has an
active program in this area.
Thanks for your patience! We are now showing the most recently answered questions at the top of the transcript. We are able to show the most recent 75 questions live here. The full transcript of all questions will be available within a week.
Arkadelphia High School, Arkansas: What is the most interesting type of cell that you have seen or worked with?
Tracy Koretsky: I have not really worked with any of the fancy cells that you see images of in biology text books. I did however work with yeast for many years, and when you mate yeast cells, you end up with a tetrad of haploid cells that you have to separate under a microscope using a glass micromanipulator. This was really challenging but I really enjoyed it.
St. Stephen School, Connecticut: Did you get good grades in science when you were in grammar school? Paula Flicker: I did get good grades in science in grammar school and in high school. However, I did not do so well in English classes. I figured that I should major in math or science in college since clearly my strength was in those areas. However, poorer grades in science in grammar school does not mean that a person cannot excel in science later on. An individual may not have seen the area of science that attracts his/her interest until later in his/her studies.
Upper Dauphin Area Middle School, Pennsylvania: Which cell is the smallest cell in the human body?
Dorit Zuk: That's a really good question because it depends on how you measure. For example, sperm cells have a diameter of 1-3 micrometers, but a tail of 50 micrometers. On the other hand, the red blood cell has a diameter of 4-8 micrometers so may be considered the smallest.
Mountlake Terrace High School, Washington: How do cells compare to plants? Do plants have cells?
Darren Sledjeski: Hi Mountlake Terrace HS. The cell is the basic unit of life. All life (at least on Earth) is made of cells. So, yes, plants do have cells. In fact, cells were named 'cells' by a
Robert Hooke who was studying cork (the bark of a tree) under an early microscope. He thought the individual compartments look like the cells monks lived in.
Mountlake Terrace High School, Washington: How many cells can we get that are bad for our body?Shireen Sarraf: Hi Mountlake Terrace High School! Great question. Bad cells can come from outside our bodies or from within our bodies. For example, infections can be caused by pathogenic (disease-causing) bacteria like Salmonella or Cholera or Staph. Usually bacteria enter the body via our mouths, but can also invade through wounds. In terms of bad cells that may originate inside our bodies, cancer arises when the DNA of normal cells accumulates mutations over time. Some cancers are strongly associated with viral infections (e.g. hepatitis B and C viruses, human papillomavirus), others are strongly associated with lifestyle factors (e.g. smoking and alcohol use), so there are known strategies for preventing certain types of cancer. However, many mutations to the DNA arise from our own processes inside our body that by chance accidentally led to the mutations occurring. These mutations can then be passed on to daughter cells during mitosis. With successive rounds of cell division, more mutations can accumulate eventually transforming a normal cell into a cancer cell. This process can take decades, which is why cancer is more often seen in older individuals.
Mountlake Terrace High School, Washington: Why don't cancer cells die off like regular cells do? Dorit Zuk: Cancer cells have mutations (changes) in their DNA that allow them to divide over and over, overcoming the mechanisms that cause regular cells to die after a certain number of divisions. For more information on cancer, go the NIH's National Cancer Institute website at:
Mountlake Terrace High School, Washington: Do silicon based life forms have cells? If so, how do they compare with carbon based cells? Darren Sledjeski: Hi. Well, we haven't discovered any silicon based life yet. So, we don't know. If you think that we are close to developing computer based artificial intelligence, then it won't be cell based....it will be chip based.
Mountlake Terrace High School, Washington: If we did not have any cells at all what would happen to humans?
Tracy Koretsky: We would not exist. We would be just a bag full of cytoplasm and organelles that would be fragile and unable to survive.
Silva Health Magnet High School, Texas: How are STEM cells being used in cancer research?
Donna Krasnewich: Stem cells are cells that are 'undifferentiated' but can become other types of cells. For example, a stem cell can become a liver cell, or a muscle cell or a nerve cell. In the case of cancer treatment, stem cells are used as a source of new blood cells. When a person is diagnosed with cancer, strong chemotherapy or radiation therapy is given until the cancer cells are hopefully killed. Unfortunately, this chemotherapy or radiation also kills the cells in our blood. A stem cell transplant is then given by IV. These stem cells then go to the bone marrow and become new blood cells that help bring the patient back to feeling healthier. This is only one of the ways that stem cells are used in cancer research.
Arkadelphia High School, Arkansas: Would it be possible to change or improve the functions of human cells?Krishan Arora: Good Question. Normal healthy human cells in various organs perform various functions and do this job in a very efficient manner. However, if the cells are diseased, scientists are working towards understanding the cause(s) of those disease and how to change or improve their function. For example, to generate healthy cells to replace diseased cells (regenerative medicine). Stem cells can be guided into becoming specific cells that can be used to regenerate and repair diseased or damaged tissues in people. For example, people who may benefit from stem cell therapies include those with spinal cord injuries, type 1 diabetes, Parkinson's disease, Alzheimer's disease, heart disease, stroke, burns, cancer and osteoarthritis. Researchers continue to advance the knowledge on stem cells and their applications in transplant and regenerative medicine.
Mountlake Terrace High School, Washington: How do blood cells die, and how fast do they die?
Mercedes Rubio: Hi! Great question. They die because they run out of oxygen.
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The cells shown here in red have many important jobs. They store and release energy, protect organs and nerve tissues, insulate us from the cold and help us absorb important vitamins. They are:
Mountlake Terrace High School, Washington: I have heard that there's bacteria on mars, if its true, how do the cells in the bacteria compare with bacteria cells on earth?
Alex Valm: Bacteria have not been discovered on Mars. Yet! But biologists are working with NASA to use remote vehicles to sample the soil on Mars for bacteria with chemical sensors and microscopes. Hoping that the cells on Mars will have things in common with bacteria on Earth, the vehicles look for specific kinds of molecules: lipids (fats), proteins and nucleic acids (DNA and RNA).
Mountlake Terrace High School, Washington: How often does a new cell get discovered?Dorit Zuk: New cells are discovered all the time. Although we know a lot about the cells in a human, there are lots of other types of cells, especially bacteria, that we don't know about. Scientists are constantly working to understand the great diversity of our world.
Mountlake Terrace High School, Washington: In how many ways do cells compare with machines? Also, in how many ways do humans compare with machines?
Susan Gregurick: I like to think of cells as biological machines. They have compartments, fluids, transport systems and even an engine. And just like the typical machines that we are used to, cells break down, overheat and have all sorts interesting behaviors. A main difference is that humans can actively operate machines, like our washing machine or our car, but our cells run without our direct input or interaction.
Check out this interesting article that will let you know about all the different molecular machines within our bodies:
And keep studying!
Mountlake Terrace High School, Washington: Why is learning about cells important in the future, even if you aren't interested in science in your future career?
Amanda Melillo: Hi! Since cells are essential for human life, it is important to have a basic understanding of them even if you are not interested in going into a career in science. Learning about cells and biology helps you learn about how systems work. This type of education can help you in what ever you end up studying. And you never know, maybe once you learn more about cells, you will find biology so exciting and decide you do want to go into a science related career! Continuous learning helps us grow!
Mountlake Terrace High School, Washington: How does the oxygen run out?Roya Kalantari: Oxygen is used up in the process of respiration. Oxygen is breathed in. As oxygen is used in the body, it reacts with carbon to form carbon dioxide. This is then breathed back out of the body.
Mountlake Terrace High School, Washington: Why is it required to study cells for science even though some students will not go into the field of Biology as their career?Patrick Brown: Great Question. Our body is made up of over 200 cell types. A basic understanding of cells, even though we may not want to pursue a career in science, allows us to be better informed citizens or to satisfy our curiosity. If you've ever had the pleasure of breathing (I hope you have), or the displeasure of having the flu or a cold -there are cells involved. Knowing how cells work will allow for better medicines to be made and for you to make better choices on medicine type, for example. Who knows? You might find out in the future that you are interested in cells.
Thanks for your interest in Cell Day! We are ready to answer your questions.
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The mitochondrion plays an important role as the cell's ....
Silva Health Magnet High School, Texas: What would you say was the most interesting experiment you have conducted? Jon Lorsch: In my lab we study how proteins are synthesized by the eukaryotic ribosome. We have learned a great deal about how the ribosome and the proteins that help it (called translation factors) find the start codon in the messenger RNA. Recently, in collaboration with a group in the UK, we used cryo-electron microscopy to determine the three dimensional structure of various 'initiation complexes' - the small subunit of the ribosome bound to mRNA, tRNA and initiation factors. Being able to actually see how this process works in three dimensions is amazing!!!
The immune system in action This action shot shows an immune system cell (purple) capturing anthrax bacteria (green). Anthrax bacteria can cause a serious illness that mainly affects farm animals and wild game. Thanks to a highly effective and widely used vaccine, the disease is uncommon in domesticated animals and rare in humans. To download a high-resolution version of this image, go to
Mountlake Terrace High School, Washington: How do regular blood cells turn into cancer cells? Rochelle Long: Most blood cancers begin in the bone marrow. Many small changes take place over time, often in the white blood cells (leukocytes). These cells grow uncontrollably. After while, the cells overwhelm the body's defenses. One category of blood cancers is called leukemias.
Mountlake Terrace High School, Washington: Where do cells get their color from? Patrick Brown: Good Question. You may have noticed that blueberries are blue, carrots are orange, most plants are green, mustard is yellow, the cells of our retina are black, eggplants are purple, all because of
pigments that are present in those cells. Many of the pigments used to dye clothing are isolated from plant and animal sources.
Mountlake Terrace High School, Washington: Hello! What causes a cell to have color?
Patrick Brown: Good Question. This is a question that others are interested in too and some have asked earlier. Scroll up through the previous chat responses and find the answer to your question there.
Magoffin County High School, Kentucky: In autoimmune diseases like lupus, what causes the body to attack its own cells?Dorit Zuk: That's a great question. Normally, our immune system can distinguish healthy cells from diseased cells or foreign cells that have invaded our body. During an autoimmune disease, the immune system loses that ability to distinguish and starts treating healthy cells as if they were diseased, i.e. attacking them. There are over 80 autoimmune diseases - see more at
Mountlake Terrace High School, Washington: when regular cells become cancer cells is it easy to misinterpret the cancer cells as something other than cancer?Paul Sammak: Yes. Cancer cells can be identified by molecular biomarkers that are unique to cancer, or by cell behavior including uncontrolled growth or movement. For some cancers there are well defined biomarkers (BRCA1 mutation for breast cancer), while other cancers are not so simple and there will be different cells in the same tumor with different molecular profiles (melanoma). Ultimately, it is the phenotype or uncontrolled behavior of cancer cells that characterizes them as harmful. At times, cancer cells can become quiet and may not move and grow detectably, making it even harder to identify which cells are normal or cancer cells. Fundamentally it is the complexity of cancer that makes it hard for any single characteristic to reliably distinguish cancer and normal cells.
Mountlake Terrace High School, Washington: Are there cells in the ocean?Amy Kullas: Hi~ Yes! There are cells in the ocean. Ocean life (such as sharks, coral, etc) are made of cells. Additionally, in the great depths of the ocean, new organisms and microbes continue to be discovered. Additionally, there are single-celled organisms in the ocean (algae, cyanobacteria).
Mountlake Terrace High School, Washington: What is the least complex cell and what are its functions?
Alex Valm: Wow what a great question. It really depends on what you consider to be a cell. Both platelets and red blood cells are not complex. They don't contain nuclei or DNA so they don't transcribe and translate genes into proteins. They have very specialized functions to carry oxygen and carbon dioxide (red blood cells) or to function in blood clotting (platelets). One cell with a nucleus and DNA and a very small genome is Mycoplasma genitalium, a species of bacteria that lives in humans.
Magoffin County High School, Kentucky: If cancer has been removed or completely eradicated from a patient, what causes the cancer to come back after a period of time?Rochelle Long: Most times, not all 100% of the original cancerous cells were eradicated. The chance of this happenings depend on many things, including the kind of cancer. The “new” cancer is typically treated as though it is a re-growth of the primary cancer, even if it occurs at another site (although testing will take place to see how the cancer is different).
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The type of cell division that creates sperm and egg cells is called mitosis.
Each shade of color in this image—blue, green, purple or pink—represents a different layer of cells in the cross section of an eyeball. At least 70 different cell types work together to transform light into sight. Two scientists from the University of Utah used chemistry, computers and artistry to produce this remarkable image. Learn more in the NIH director’s blog post at
To see another image of the many cell types in the eye—including cones that allow us to see color and rods that help us see under low-light conditions—go to
http://www.nigms.nih.gov/education/life-magnified/Pages/9_bottom_eye_nerve_cell.aspx. High resolution versions of both images are freely available for download from the Life: Magnified collection at
Mountlake Terrace High School, Washington: What are some of the biggest uses of CRISPR in the future? Roya Kalantari: Great question!
CRISPR has the biggest potential in the near future to impact the creation of animal models to study disease. CRISPR is currently used most often in cell culture, and has already begun to be used in several animal models, but it's full potential hasn't yet been reached. There are many model organisms ranging from flies, to mice, to pigs, and CRISPR hasn't yet been refined to work well in all those model organisms. Researchers are working on ways to tweak CRISPR so that it can work efficiently in each animal type. Once they can do that, it will drastically reduce the time that it takes to make animal models to study various diseases, especially complex ones. Because previous gene editing methods weren't very efficient and had many unwanted effects because of targeting the wrong part of the genome, CRISPR will also make it possible to create disease models that weren't possible before (although CRISPR isn't perfect either). With the ability to make many more disease models in a shorter amount of time, scientists will be able to study diseases and test potential new drugs more quickly, and hopefully accelerate the process of finding treatments and cures.
Your eye contains at least 70 different types of cells
Mountlake Terrace High School, Washington: What is your opinion on how life on Earth started? Jon Lorsch: The prevailing idea for how life on earth started is that organic molecules such as amino acids and nucleotides formed from less complex molecules through repeated cycles of heating, lightning blasts and catalysis by inorganic compounds found in the environment. These building block molecules floated around in watery places and eventually formed polymers such as proteins and RNA. Some of these molecules ended up inside tiny membrane balloons called vesicles that were formed through similar process to those described above for nucleotides and amino acids. Because RNA can serve both to carry genetic information and catalyze reactions, one hypothesis is that there was an 'RNA World' before proteins became major players. In this RNA World, RNAs replicated themselves inside of vesicles and then eventually recruited proteins to help them. The modern cellular protein synthesis machine - the ribosome - is made of an RNA core with proteins bound to it, which suggests the primordial protein synthesis machine might have been made just of RNA. There are of course other ideas for how life started, but the RNA World hypothesis is consistent with a number of observations and experiments.
Clarkstown High School North, New York: Can a mitochondrion live outside of a cell? Roya Kalantari: No, mitochondria cannot live outside of cells. They are codependent on one another.
Clarkstown High School North, New York: What makes the HeLa cells unique?
Amy Kullas: Hello students of Gertzer Biology. HeLa cells are an immortal cell line, meaning that they continue dividing. They were originally isolated from a patient at Johns Hopkins and have forever changed science! Many labs routinely use these cells in their research. If you want to learn the story behind the HeLa cells, 'The Immortal Life of Henrietta Lacks' book may be of interest.
Mountlake Terrace High School, Washington: What is the most complicated cell known? What are its functions? Paul Sammak: You might get different answers depending on the scientist that you ask! Neurons come to mind (pun not intended) because they are super specialized for communication. They are asymmetric, and communicate electrical and chemical signals in one direction; from dendrites to axons and via synaptic connections to the next neuron. If you are a developmental biologist or an mammalian embryologist, you might vote for a fertilized egg, because of it's grand potential to form every different type of cell in the body (and placenta). I would vote for platelets as the least complicated cell, because it's lost its nucleus and is specialized for getting tangled up with each other to form blood clots and stop bleeding.
Silva Health Magnet High School, Texas: Was it hard for you to understand how the cells work?
Susan Gregurick: I thought that studying how cells work was both a challenging and fascinating adventure. I took my first class in cellular physiology as a sophomore in college and I have fond memories of learning all about the Krebs, or citric acid cycle. Even though I truly loved learning about cellular processes, I went on to study chemistry. However, I always find great uses for my old text book, Cell, and now my son uses this book.
Silva Health Magnet High School, Texas: Can GMO food cause allergies reactions?
Rochelle Long: Allergic reactions occur when we react to proteins in the foods. It is a complex interplay between those proteins and our own immune systems, and no two people are alike. If a genetically modified food (GMO) presents a new protein, an allergic reaction is theoretically possible, but fortunately, it’s not common.
Magoffin County High School, Kentucky: How does the human body differentiate between foreign cells and those of the human body? How does the immune system know what cells to attack and what cells to leave alone? Dorit Zuk: Foreign cells contain substances (often proteins) called antigens that stimulate our immune cells to produce antibodies. These antibodies tightly bind to the foreign cell, tagging it for attack by other parts of the immune system.
Mountlake Terrace High School, Washington: How does learning about Cells prepare us students for when we're adults? Mercedes Rubio: Hi! What a fantastic question! I could give you a response about how fun it is to learn about cells or how wonderful cells are. However, I don't think it that is what you are hoping for. So I will answer the in the following way -- the problem solving skills that you gain from your biology, chemistry and algebra courses are part of your toolkit to adulthood. It is important to think logically, to follow a process/method, and to entertain an alternative perspective or point of view. My job requires me to problem solve daily, and I attribute my ability to do this well to learning about cells.
Magoffin County High School, Kentucky: How is the nerve signal interpreted by the cell body of a neuron, and how does the cell body decide which axon terminal the signal will be sent? Moderator Team: Nerve cells (neurons) receive chemical signals, convert them into electrical signals, and then back into chemical signals that are transmitted to adjacent cells. In the body, nerve cells make dozens of contacts with adjacent cells, each of which send a stimulating or inhibiting signals to their neighbors. The relative balance of these signals control how signals are transmitted within axons. Thank you for a great question!
Germantown Friends High School, Pennsylvania: Does your career typically keep you in one place or are there traveling opportunities within your career field?
Patrick Brown: Nice question, Friends at Germantown. Scientists have many opportunities to travel. There is a lot of collaboration in science. On occasion, it may be necessary to fly to meet a collaborator in order to get some time on expensive instrumentation (like a synchrotron) or to borrow someone's expertise. Frequently, scientists travel to conferences or annual meetings (which can be almost anywhere in the world) and they present a poster or give a talk to explain their latest research results. Being able to travel and meet new people in new places is one of the really nice things about being in science.
Germantown Friends High School, Pennsylvania: What happens when a person has too many or not enough chromosomes, missing parts of chromosomes, or mixed up pieces of chromosomes? Jessica Faupel-Badger: Great question! Differences in the number of chromosomes are related to a wide range of human diseases and conditions. Perhaps one of the most well-known is Down Syndrome, where individuals have part of an extra chromosome 21. Cancers also show variation in the number of chromosomes. For example, individuals with Chronic Myeloid Leukemia have a chromosomal translocation where part of chromosome 9 is fused with chromosome 22. Interestingly (particularly for your school), this is known as the Philadelphia chromosome!
Germantown Friends High School, Pennsylvania: How do cells die? Roya Kalantari: Cells can die in many different ways. They can die from an infection, from physical damage that causes them to break open, lack of oxygen, or heat and cold to name a few. Cells can also die through a process called apoptosis, which is a process that the cell is programmed to do if it decides that there is something wrong, or if the cell is no longer needed (such as during development).
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Which cells communicate using chemical messages?
Germantown Friends High School, Pennsylvania: Can you pinpoint points on cells to weaken eliminate them? If so, can we apply this to cancer research? Rochelle Long: Absolutely! This is part of the growing field of pharmacogenomics, or precision medicine. In targeted cancer therapy, the tumor cells are analyzed for their molecular characteristics. Proteins which are found to be present on the cancer cells (and are NOT present in normal cells) are where the cancer cells are vulnerable. To learn more, see
Mountlake Terrace High School, Washington: Is there any matter whatsoever that is not made of cells?Mercedes Rubio: Hi! Great question! Organic matter are made of cells. This means that inorganic matter lack cells.
We are ready to answer your questions! Thanks for your interest in Cell Day.
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Among its many responsibilities, this type of cell produces bile (a liquid that aids in digesting fats). It also detoxifies blood and chemically processes hormones, medicines and alcohol. It is found in:
Magoffin County High School, Kentucky: What changes in the autoimmune cells that causes them to attach and attack normal body cells?
Dorit Zuk: Thanks for your interest in the immune system. It is a fascinating part of our body. Scientists are still studying exactly what happens to cells in the various autoimmune disorders. In general, there may be a number of changes that could trigger such a response. For example, a normal cell could be altered due to mutations in its DNA and it suddenly looks like a foreign cell - i.e. presents a foreign antigen - and gets attacked. Or, the immune cells change (mutations again) and start producing antibodies that recognize a normal cell as foreign.For more information check out
Germantown Friends High School, Pennsylvania: How did prokaryotes and eukaryotes get their name? Alex Valm: What a great question about the history of science! The names prokaryote and eukaryote is generally attributed to Edouard Chatton in 1937. The idea that all cells could be divided into two groups was accepted by most biologists until the 1970s when Carl Woese proposed that it makes more sense to consider three major groups of life, based on ribosomal RNA sequences. Take a look at this link to learn more about Carl Woese:
King School, Connecticut: How are stem cells derived from humans and used for research?Paul Sammak: There are different kinds of human stem cells that are derived from different sources. There are adult stem cells in many tissues such as bone marrow, muscle, fat, intestine, skin, brain, etc. that are multipotent and can form a few different cell types. These cells will be important for tissue engineering and treating disease. Embryonic stem cells are pluripotent meaning they can form any type of cell in the body. Recently, a new type of pluripotent stem cell, the induced pluripotent stem cell (iPSC), has become very exciting to researchers. They can be derived from any individual from many different kinds of body cells including skin, or internal organs. They are genetically modified to become pluripotent by expressing 4 transcription factors that dedifferentiated them into primitive, pluripotent stem cells. They are unique because they are genetically matched to the original donor and have great potential for therapeutic treatment of an individual. iPSCs derived from someone with a genetic disease can help us find breakthroughs for treating disease too.
Coppell Middle School North, Texas: Is it possible that a cell will survive if one organelle never existed?Dorit Zuk: That's a great question! If a cell has a specialized function, it might not need all the organelles and might even benefit from losing some. For example, the red blood cells of humans (see image) ditch their nuclei during their maturation to make more space to carry hemoglobin, the molecule that transports oxygen all around the body. Lacking a nucleus also allows a red blood cell to bend into a lozenge shape so it can slip through narrow capillaries. Since mature red blood cells don't divide, they don't need the genetic material that is stored in the nucleus.
Germantown Friends High School, Pennsylvania: How does a cell know what particles to allow into/ out of the cell?Jon Lorsch: Proteins on the surface of cells, called receptors, bind specific molecules. Each receptor has a certain shape that allows it to interact with a particular molecule, like a key fitting into a lock. When the right molecule binds the receptor, it triggers the cell membrane to envelop the molecule and receptor, bringing them into the cell in a membrane balloon called an endosome. When the endosome opens up, it can deliver the molecule into the cell. This overall process is called endocytosis. Other proteins, called channels, form gated passageways through cell membranes and can let molecules and ions flow in. Other proteins can actively pump molecules or ions into or out of cells. Cells can synthesize proteins and secrete them into their environment. The protein synthesizing machine - called the ribosome - can thread proteins that it makes into the membranous endoplasmic reticulum. From there, the proteins travel to the Golgi apparatus in membrane balloons called vesicles. In the Golgi the proteins get sugars added to them and then exit the cells inside of vesicles. This process is called exocytosis.
Coppell Middle School North, Texas: What is the best microscope to view cells? Alex Valm: This is such a great question and something I am very interested in myself. There are many different kinds of microscopes that have specific qualities that make them best for answering different kinds of questions. Generally there are two main kinds of microscopes: electron microscopes and light microscopes. Electron microscopes allow the greatest magnification and resolution of small objects--down to the scale of molecules, but they have two major limitations: 1. They can only be used on dead cells. 2. They cannot be used with labels to identify specific parts of the cell. Light microscopes have lower resolution, but they can be used on live cells. Fluorescence microscopy allows scientists to label specific proteins or other structures in the cell and recent advances in light microscopy allow 'super resolution': the ability to see objects smaller than the light microscope resolution limit. The 2014 Nobel Prize in Chemistry was given to the inventors of super resolution microscopy. You can read about it on their website:
Coppell Middle School North, Texas: What would happen if there was a new type of organelle that right now does not exist, but was formed within the next few years? How would that affect us?
Rochelle Long: Anything is possible! Let’s think about the organelles that exist right now and what they do. Here is a fun PBS movie clip that shows some of the cells’ most important functions in action:
http://mpt.pbslearningmedia.org/resource/tdc02.sci.life.cell.organelles/organelles-in-the-cytoplasm/. You might be interested to know that our Institute, NIGMS, funds research to develop better ways to look into cells (microscopy) so if a new organelle is going to be discovered, scientists will find it.
Lakeview Middle School, Indiana: What organ system has the most cells? Jessica Faupel-Badger: This is a great question. I am guessing it would be the gastrointestinal tract given how long the intestine is. And, if you include all (human and non-human) cells, the number of cells in the gut would increase exponentially given the number of bacteria functioning at the lining of the gut. It is estimated that there are 10 times more prokaryotic cells in the human body (mostly in the gut) than there are human cells.
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This image shows the embryo of an increasingly popular model organism. Because of its rapid growth and see-through embryo, the creature is ideal for scientists studying how organs develop. The organism is a:
Just 22 hours after fertilization, this zebrafish embryo is already taking shape. By 36 hours, all of the major organs will have started to form.
Here's another beautiful picture of a developing zebrafish. It was taken by Jessica Plavicki, a developmental biologist at the University of Wisconsin–Madison. Plavicki uses zebrafish to study the impact of environmental contaminants such as dioxins on the developing embryo.
High-resolution versions of these and many other cellular images are freely available from the Life: Magnified collection at http://www.nigms.nih.gov/education/life-magnified/pages/default.aspx.
Coppell Middle School North, Texas: Is it possible to live with limited cells?
Roya Kalantari: No, it is not possible to live with limited cells. There are certain parts of your body where the cells almost never turn over, but other parts of your body have cells that die and regrow every day. Things like your skin or liver have cells that are constantly dying and growing as they get damaged or old. If you had limited cells, those parts of your body would not be able to heal damage. If you got a cut or an infection, those cells that died in the process would never be able to grow back!
Lakeview Middle School, Indiana: Can we create synthetic cells? Susan Gregurick: Yes! We can, well sort of. Craig Venture (of JCVI) created the first self-replicating synthetic bacterial cell back in 2010. Okay, he did it by modifying the
Mycoplasma mycoides genome (which is the smallest genome) and placed this genome into a recipient cell. It worked! And his research built a foundation to new research directions.
Lakeview Middle School, Indiana: Do we know everything about the cell?
Amy Kullas: Hi. We do not know everything about the cell. This is why it is so exciting to be a scientist! We continue discover new aspects of cells in addition to furthering the understanding of cellular components. Some of these discoveries may be understanding how certain genes are regulated or even figuring out what genes do.
Coppell Middle School North, Texas: Do the Limbic System, Thalamus and the Hypothalamus have cells? If they do, what are they? Patrick Brown: Nice question, NORTH Science 7! There are several types of cells in the limbic system, including neurons, glial and mesenchymal cells. Their functions include receiving signals from other neurons cells, immune response activity and scavenging, and controlling blood flow in the brain.
Coppell Middle School North, Texas: Could there be other types of cells that have not yet been discovered?
Jon Lorsch: Yes, definitely! We only know a fraction of the organisms that live on earth, so there are certainly cells left to discover. Even within our own bodies, it is possible that there are types of cells that we have not yet recognized. You may well be the person who discovers an important new cell type.
Loudoun School for the Gifted, Virginia: Is there a typical membrane potential for non-neuron cells? Why is the resting membrane potential negative?Dorit Zuk: All cells have a potential difference across their plasma membrane. This potential ranges from about range from –40 mV to –80 mV. The potential does not change much in non-neuronal or muscle cells. In neurons at rest, there are relatively more sodium ions outside the neuron and more potassium ions inside that neuron leading to a negative resting potential.
Davies Career & Technical High School, Rhode Island: During the cell cycle there are G1 and G2 phases. During these gaps, there are still important activities occurring. Can you give us some examples of these activities? Rochelle Long: The stages in the cell cycle are G1, S, G2, M. During the first gap (G1) the cell is growing in size and making new organelles. During the second gap phase (G2), the cell is preparing for division. You can find lots of great diagrams of the cell cycle on the web; here is just one:
Mountlake Terrace High School, Washington: Approximately how long does it take for a cell to repair damage as well as fully heal?
Susan Gregurick: Once cells realize that damage has occurred, they will stop dividing and begin to excise the damaged DNA. It’s as if the damage itself activates new programming process within the cell and the response is very quick. By the way, this is an active area of scientific research and I imagine that the specifics will depend the cell type and extent of damage.
Lakeview Middle School, Indiana: What diseases besides cancer, are caused by cell mutation?Roya Kalantari: Mutations in cells can cause many kinds of diseases. A common example of a mutation that actually causes a change in the way a cell looks is sickle cell anemia. In sickle cell, red blood cells actually take on the shape of a sickle (like a crescent moon). This lowers the ability of the red blood cell to carry oxygen and deliver it throughout the body. What is more common are genetic mutations that cause changes in the proteins they code for, that may not really affect how a cell 'looks.' Diseases like Huntington's Disease, Parkinson's Disease or Duchenne Muscular Dystrophy are some of the examples of genetic disorders that come from mutations.
Lakeview Middle School, Indiana: What happens to a cell after it dies?Jessica Faupel-Badger: Great question. In our bodies, cells undergoing a process of programmed cell death, known as apoptosis, are engulfed by immune cells known as macrophages. Even though this is cell death, there is a highly coordinated program of signaling pathways that control how the cell is fragmented.
Mountlake Terrace High School, Washington: Have you ever interacted with synthetic cells? If so, what is the process of creating a synthetic cell? Jon Lorsch: It depends what you mean by a synthetic cell. When I was in graduate school, I worked with a man named Jack Szostak whose goal is to make a cell from scratch - a truly synthetic cell. He is not there yet, but he has learned a lot of amazing things as he tries to do it. For instance, RNA can catalyze all kinds of different reactions, something few people had believed possible. In the lab we frequently use cells that we have added new genetic material to. For example, we often add DNA circles called 'plasmids' to bacteria to get them to synthesize proteins that we want to purify and study. The plasmids have a gene for the protein we want and the bacteria obligingly make it for us. We get the plasmids into the cells either by treating them with chemicals or using electricity to blast the DNA in. It's pretty cool it works!
Lakeview Middle School, Indiana: How much bigger is a plant vacuole compared to an animal vacuole?
Paul Sammak: Plant and animal vacuoles have different functions, which influences their size and contents. Plant vacuoles are used for storage and for containing water that stiffens the cell wall with high internal pressure. A single central vacuole in a plant cell can be up to 80% of the cell volume. The pressure helps plants cells form stiff building blocks that create structures such as stems and leaves. These structures can be later stabilized by protein and cellulose fibers in the cell wall. In animal cells, there are many more vacuoles than in plant cells but they are small compared to the plant vacuole. Some cells have no vacuoles. They play a role in storage, waste disposal of degraded cell components, and in transport of molecules in and out of the cell. Specialized cells have vacuoles for secreting protein from organs that create hormones proteins or lipids used elsewhere in the body. Other cells in the immune system have large vacuoles for internalizing foreign particles in a process called phagocytosis.
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Which is not part of the cytoskeleton?
Mountlake Terrace High School, Washington: Are new types of cells still being discovered?
Alex Valm: The answer is YES. New types of cells are being discovered constantly in the human body and in the environment. For example, scientists recently discovered a new kind of immune cell that specifically protects the liver from infection. The discovery of pluripotent stem cells in the 1980s has revolutionized how we think of human biology and how we might be able to treat diseases. In short, there are trillions of cells in the human body and there are potentially many different kinds of undiscovered cells. Perhaps you will be the biologist to discover an important kind of cell in the human body that will allow us to understand health!
Mountlake Terrace High School, Washington: Can you elaborate more on central dogma?
Patrick Brown: Good Question, The central dogma of biology is the classic view of how proteins are made from our DNA. It has been explained that our
transcribed into messenger
RNA gets translated into
Loudoun School for the Gifted, Virginia: Why do neurons utilize both K+ channels and Na+/K+ ATP-ase pumps to establish a negative resting potential? It seems like such an ineffective method.
Dorit Zuk: Ion channels and pumps function very differently. Channels, when open, allow ions to passively diffuse in a thermodynamically optimal direction while pumps work actively to send ions across membranes, even against a gradient. Scientists traditionally thought these two types of mechanisms have very different structures and functions but are now finding that they have a lot in common. Take a look at this review for more information
St. Charles School, New Mexico: How are scientists able to calculate the density of the nucleus and other organelles? Susan Gregurick: This is a great question! You could first approximate this as a volume calculation, but the organelles and cellular compartments are filled with more than just water. So you need to take into account the volume of the cell, plus the fluid density and an estimation of particle masses.
How would you measure the density? There are some very delicate instruments that measure differences in buoyance mass. Check out this paper from the National Institute of Standards and Technology,
It’s a nice read.
Lakeview Middle School, Indiana: Can binary fission result in trinary fission?
Mercedes Rubio: Hi. Thank you for your questions. Typically at replication, two identical daughter cells are generated from the parent cell. There are times when cells mutate in ways inconsistent with the typical cell division process. When this occurs it is a result a division error.If you are speaking, for example, about nuclear fission then it is possible for a nucleus to be split into several smaller fragments. These fragments, or fission products, are about equal to half the original mass.
Francis Howell Central High School, Missouri: How do prokaryotes protect their DNA without a nucleus? Jon Lorsch: Good question! Most DNA in bacteria is circular, and wound up ('supercoiled') the way an old-fashioned telephone cord used to get (you probably have never seen that, but if your teacher is old enough he/she has). This winding helps compact the DNA. The DNA also binds to a number of proteins that further compact it, which lets it fit inside the cell and helps protect it from damage. Although there is no nucleus, the compacted bacterial DNA sits in a special region of the cell called the nucleoid. If the DNA becomes damaged there are enzymes that will actually repair it.
Mountlake Terrace High School, Washington: Why are HeLa cells immortal? Jessica Faupel-Badger: Thanks for this question! HeLa cells are cervical cancer cells that have been growing in culture dishes in laboratories since the 1950's. It isn't that any one cell is immortal but rather that these cells continue to divide and produce daughter cells. In this way, the HeLa cell line is immortal. Being cancer cells, these cells have acquired numerous genetic mutations where they now have the ability to replicate indefinitely. Being able to culture human cancer cells in the laboratory was a huge advance for cancer research. These cells have been grown in laboratories all over the world and contributed to many advances in human health, including some not related to cancer.
Mountlake Terrace High School, Washington: Hypothetically, when someone gets a laceration and gets stitches and then the skin starts to heal and grow back, is the scar caused by the growth of new skin just as healthy as normal skin? Why are scars a different texture/color/etc. from normal skin?
Rochelle Long: Scar tissue may appear to be different, depending upon the kind and severity of the injury you are recovering from, the location on your body, your age and overall health, and your skin type and color. Some skin types produce keloid scars (thickened skin), or hypertrophic scars, or contractions or adhesions. These are caused by collagen overgrowth, and it seems that the fibroblasts are overactive. The precise causes are not known, but it depends upon the genetics of the individual. Fortunately, the main concern is usually the appearance, and the tissue is not unhealthy.
Mountlake Terrace High School, Washington: What is it about viruses that make them unable to be cured?
Amy Kullas: Hi. It is important to note: Not all viruses cause disease. Viruses are really tiny agents that infect cells, including animal cells, plants cells and bacteria. They can replicate only inside a living cell. There are different types of viruses: single stranded or double stranded as well as be made of RNA or DNA. Some viruses, such as the influenza virus, which causes flu are able to change how their outside looks to our immune system making them look like a new virus to us. Additionally, viruses replicate quickly and are constantly changing allowing them to no longer respond to certain anti-viral treatments. Further, there are viruses that we are infected with that remain dormant for years before we have a flare up. An example of this is the chicken pox coming out later in life as shingles.
Lakeview Middle School, Indiana: What happens in interphase that can lead to cancer cell mutation? Roya Kalantari: During interphase, the cell is preparing for division by making copies of its DNA and growing up the cellular components needed for the cells to divide during mitosis. When the cell is replicating its DNA, things can go wrong and the cell can make the new copy of DNA incorrectly. This mutation in the DNA, if not recognized by the cell as a problem, allows the cell to replicate with the mutation and create more mutated cells, which then become cancer.
Mountlake Terrace High School, Washington: How do cells make "decisions?" Obviously, they don't have a consciousness or a brain, but how do they as an entity "decide" to move, or eat, to engulf a foreign invader, etc...
Paul Sammak: Think of the cell as a machine that can do work or perform various functions. This machine is controlled by regulatory machinery that uses external signals to throw switches on or off. For example, cell surface receptor molecules receive extracellular ligands, are then internalized to control gene expression. New protein expression can change cell function (hormone secretion or cell movement). There are baseline machines that are active to maintain life without specific extracellular signals, so an unstimulated cell is not inactive.
Mountlake Terrace High School, Washington: Once the tumor is removed from a cancer patient, how can the cancer cells come back?Rochelle Long: Probably, not every single original cancerous cell was removed with the tumor. The chance of this happening depends on many factors, including the kind of cancer. The cancer that comes back is usually treated as though it is a re-growth of the primary cancer, even if it occurs at another place in the body.
Mountlake Terrace High School, Washington: How far have we come to finding a cure or at least better treatments for Parkinson's disease? Jessica Faupel-Badger: Thanks for this question. Here at the National Institutes of Health, we have 27 different Institutes supporting research in a wide range of areas. The National Institute of Neurological Disorders and Stroke (NINDS) funds a lot of research in this area and features advances in Parkinson's Disease research on their website.
Only 15 minutes left in Cell Day! We are still accepting questions. Thanks again for your participation.
Mountlake Terrace High School, Washington: How did you know that biology was the career for you? In other words, what motivated you to become a biologist?
Amy Kullas: Fantastic question! I remember being in my high school biology class, gazing through a microscope, and seeing the mixture of beautiful purple and pink cocci after performing my first Gram stain. It was at that moment I got hooked in science. I majored in microbiology in college and then went on to graduate school. There are many different career options in the overall field of biology and I wish you the best in your future!
Mountlake Terrace High School, Washington: So far to my understanding is all life is based upon the chemistry of carbon. I was wondering for a while after being introduced to this concept within Chemistry if there was a possibility for silicon based life due to their ability to form similar bonds to carbon? I'm guessing that the problem would lie with using liquid water and would instead have another liquid basis of some sort, maybe methane.
OCPL Team19: Thanks Mountlake Terrace High School for the question!
Our scientist, Dr. Darren Sledjeski, answered a similar question earlier. You can scroll back through the transcript; I also pasted it below for your convenience.
Mountlake Terrace High School, Washington: Do silicon based life forms have cells? If so, how do they compare with carbon based cells?
Darren Sledjeski: Hi MTHS. Well, we haven't discovered any silicon based life yet. So, we don't know. If you think that we are close to developing computer based artificial intelligence then it won't be cell based....it will be chip based.
Mountlake Terrace High School, Washington: What is cellular respiration?
Patrick Brown: Hi. That is a good question. Respiration is the chemical process that cells use to convert their food (nutrients) into energy that can be used for cellular process (movement, breathing, thinking....). For example glucose can be broken down in the presence of oxygen to produce energy (and carbon dioxide, and water).
Check your cell IQ!
Researchers have learned how to use florescent proteins to highlight specific cellular structures. The first fluorescent protein used for this purpose is known as Green Fluorescent Protein (GFP) and it was isolated from:
Francis Howell Central High School, Missouri: Some bacteria can do photosynthesis (e.g. cyanobacteria) but they are prokaryotes, so they can't have chloroplasts. How can they perform photosynthesis without chloroplasts? Related, how do bacteria get energy from sugars if they do not have mitochondria?
Alex Valm: This is a great question. It's true that some bacteria can do photosynthesis and most can do cellular respiration. They can do these functions without chloroplasts and mitochondria because they have all the enzymes and electron carriers necessary in their cell membranes. So instead of doing these processes inside organelles, they do them in the cytoplasm and cell membrane. In fact, according to the endosymbiont theory, chloroplasts and mitochondria were generated when an archael cell engulfed ancient bacteria, giving rise to the first eukaryotic cell.
Check your cell IQ! Which organelles are sometimes described as cellular power plants?
Mountlake Terrace High School, Washington: All cells in an embryo have the same heredity, yet they develop into different tissues and organs and organ systems. What is the process by which this happens? Dorit Zuk: That's a great question! This process is called cell differentiation. Specific cells turn on different combinations of genes which make proteins that allow them to develop into specific tissues and organs. For example, cells that will develop into muscle cells start expressing genes that code for specific proteins such as myosins, which are required for muscles to contract. Cells that will develop into red blood cells do not express the myosin genes but turn on the gene for hemoglobin.
Mountlake Terrace High School, Washington: Why does DNA contain Thymine but RNA contains Uracil? Jon Lorsch: Awesome question. The answer is really fascinating. It turns out that the nucleotide base cytosine in DNA can spontaneously convert to uracil by losing a molecule of ammonia. If uracil was normally in DNA, the cell would have no way of knowing that this was wrong when it happened, and when the DNA was replicated it would result in a mutation from a C to a U at that position. That could be bad, resulting in diseases such as cancer. But since DNA contains T instead of U, when the cell finds a U in its DNA it knows not only that that is wrong, but that that position used to be a C!!! How cool is that? There are enzymes in the cell that scan the DNA looking for U bases and cuts them out when it finds them, so they can be repaired and replaced with Cs. These enzymes are called Uracil-DNA Glycosylases. We have this enzyme in our cells - a very good thing! Isn't biology cool?
Mountlake Terrace High School, Washington: How do cells decide what direction to move in? Jessica Faupel-Badger: Cells have receptors on the cell surface. These receptors will interact with chemicals in the environment. The cells will move along a gradient of these chemicals. It is interesting to see a movie of cells responding to one of these gradients and moving. You will see a leading edge where it looks like the cell membrane is rippling and a lagging edge that is calmer.
Mountlake Terrace High School, Washington: What is the practical difference between bioengineering and biotechnology?Roya Kalantari: Good question! Bioengineering and biotechnology are very different fields.Bioengineering is usually focused on the idea of creating artificial organs and limbs. Bioengineers work on creating things such as prosthetics or implants (like pacemakers) that help people who have been injured or have health complications. Biotechnology is mainly focused on creating instruments that scientists and doctors use. These instruments can be things like MRIs, microscopes, or X-ray machines.
Mountlake Terrace High School, Washington: What is a good way to remember all the organelles and their functions? Dorit Zuk: Great question! The best way to remember the organelles is to really understand what they do. You can look for pictures and examples in different animals, or even build your own models. Good luck!
Mountlake Terrace High School, Washington: Can an individual's diet be a cause or factor in getting cancer? Mercedes Rubio: Hi. I love your question. A well-balanced diet and a healthy lifestyle (physical activity, plenty of sleep, positive outlook in life, etc.) are key factors in minimizing the risk of cancer. A diet high in fat and sugar tends to increase peoples' weight and being overweight has been associated with an elevated risk of a number of cancers. Keep in mind that you are what you eat!
Check your cell IQ! The fatty covering that surrounds nerve fibers and dramatically speeds the transmission of nerve signals is composed of
Check your cell IQ!
Which of the following is not a phase of mitosis?
Mountlake Terrace High School, Washington: Could you elaborate more on the laws of thermodynamics and how they pertain to real life examples? How are we able to utilize these laws for our benefit?
Susan Gregurick: I love the laws of Thermodynamics. Has your teacher illustrated the Thermodynamic box-this is a great technique for remembering Maxwell’s equations. Anyway, my favorite law is the second law of Thermodynamics: The Entropy of an isolated system never decreases. Well, entropy is a measure of disorder. So then I can ask you a question: proteins usually fold up from a denatured state of maximum entropy to a folded state of minimum entropy! How does this NOT break the second law of thermodynamics. You will get the answer by looking at Maxwell’s equations, and think about the contribution of entropy and the contribution of enthalpy in protein folding! Good luck!
Mountlake Terrace High School, Washington: What are considered to be the most debilitating genetic disorders and what chromosomes are associated with? Amy Kullas: Great question! I would direct you to one of the other IC's websites:
https://www.genome.gov/10001204/. Differences in the number of chromosomes are related to a wide range of human diseases and conditions. Cancers can also show variation in the number of chromosomes. For example, individuals with Chronic Myeloid Leukemia have a chromosomal translocation where part of chromosome 9 is fused with chromosome 22.
Mountlake Terrace High School, Washington: What two taxonomic domains are divided based on the presence, or absence, of peptidoglycan?
Alex Valm: One way of dividing life into two groups is to consider them as either prokaryotes or eukaryotes. With this division, prokaryotes are small cells with no nuclei or membrane bound organelles and they do have a cell wall made of peptidoglycan. Eukaryotes are large cells with nuclei and membrane bound organelles and no cell wall. Modern biologists have proposed a different view of life with three divisions: bacteria, archaea and eukarya. Instead of phenotypic differences, these categories are defined by nucleic acid sequence: namely the ribosomal RNA sequence.
Mountlake Terrace High School, Washington: How does RNA know when to stop copying? And how do they tell the difference between introns and exons? Jon Lorsch: There are signals at the end of a gene that tell the RNA polymerase to stop. In eukaryotes, this signal can tell the cell's machinery to add a poly(Adenosine) tail to the RNA if it is a messenger RNA. Introns and exons are also recognized by special sequences that tell the spliceosome - the machine that splices the exons together - where the intron/exon junctions are. Good question!
Mountlake Terrace High School, Washington: Do we have the technology to reprogram cells to act like other different types of cells? If so, can you give me a general synopsis of how it works?Rochelle Long: You are probably thinking about induced pluripotent stem cells (iPS). The methods are becoming better understood, and right now it requires specialized labs, but they can differentiate iPS into different cell types such as nerve cells or cardiovascular cells for experiments. Try reading at this link for an overview of the process:
Mountlake Terrace High School, Washington: What would a chip based life form look like? What would it do? How would it act? OCPL Team19: Hi, thanks for participating in Cell Day 2016! We answered similar questions earlier, please scroll back through the chat or check out the 2016 transcript (which will be posted later next week).
Loudoun School for the Gifted, Virginia: Negative membrane potential followup: Why does the difference in sodium and potassium concentrations, across the membrane exist ?Paul Sammak: The potassium gradient across the plasma membrane is responsible for most of the resting membrane potential and is regulated by the sodium potassium exchanger and other ion channels. Maintaining this gradient is energetically expensive and can take up to a third of the ATP expenditure of the cell. The purpose includes maintaining cell volume, osmolarity and shape, and also as an engine for molecule transport in and out of the cell. It is also involved in regulating cell signaling by calcium and other mechanisms.
Mountlake Terrace High School, Washington: How involved are cells in the formation and recollection of memories, if at all? Do cells themselves have any influence over how we behave as individuals?Mercedes Rubio: Hi! Have you ever been hungry? If so, then you have a wonderful example of how cells influence human behavior. Bon Appetite!
Mountlake Terrace High School, Washington: How realistic (and also unrealistic) is the media's perception of epidemics, health concerns, biostatistics, and etc... ? Do you see the media misinterpreting you work often? Dorit Zuk: The media has the difficult task of taking complicated scientific issues and explaining them in way that everyone can understand. Mostly they do a good job with this, but sometimes some of the nuances and details get lost in the process.
Mountlake Terrace High School, Washington: How many organelles are there actually? Yes, in biology we're taught a few, but are there more?Paul Sammak: We've identified membrane bound organelles that have defined contents or interact with other structures for transport, cell assembly or signaling. Other organelles are protein oligomeric structures such as microtubules, and other components of the cytoskeleton. Many structures have been identified by microscopy but unpublished stories have suggested that there are other compartments that have yet to be identified for their function or structure.
We are putting the final touches on the last few answers... thank you again for your support of Cell Day!
Mountlake Terrace High School, Washington: May you please discuss the process of semi conservative replication? Jon Lorsch :Semiconservative replication means that each strand of DNA gets copied to make a daughter strand, so then there is one new strand and one old strand in the two new double-stranded DNA molecules.
Silva Health Magnet High School, Texas: What is amyloidosis and why is it considered a cancer? Rochelle Long: It’s not really a cancer, but it is a growth disorder of cells. There are a couple of different types, and generally they involve clumps of cells forming that are produced by immune cells. Try reading here for more information:
Mountlake Terrace High School, Washington: Among all the scientists currently on right now. Who among you is the best? Jon Lorsch: We are like an all star team!
Mountlake Terrace High School, Washington: What do you think is the best thing about being a biologist? Why do you love your job so much? (Assuming that you do)
Patrick Brown: I love that question. And, I love being a scientist. There are so many things that I like about my career choice. The answer is simple—I like learning! I like learning about different living organisms and how they may be the same or different. I also really enjoy the multi-cultural aspect of science. I get to interact with so many different people from different parts of the world who are all studying different aspects of science that are just as interesting as my own, and we are all interested in knowing more about life.
Mountlake Terrace High School, Washington: What is your favorite piece of literature that has to do with cells? Mercedes Rubio: Some of my colleagues are enjoying 'The Emperor of All Maladies: A Biography of Cancer'
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1/23/2020 12:47 PM
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