Have you ever wondered why your cells don’t spill into each other or what keeps your skin separate from your blood? The answer to both is lipids—a diverse group of organic compounds that don’t dissolve in water. They’re one of the four major building blocks of our bodies, along with proteins, carbohydrates, and nucleic acids. Types of lipids include:

• Fats, necessary for our bodies’ long-term energy storage and insulation. Some essential vitamins are fat soluble, meaning they must be associated with fat molecules to be effectively absorbed.
• Phospholipids, which make up a large part of cell and organelle membranes.
• Waxes, which help protect delicate surfaces. For instance, earwax protects the skin of the ear canal.
• Steroids, including cholesterol, a precursor to many hormones, which helps maintain the fluidity of cell membranes.

When you encounter the word expression, you may think of a smile, a grimace, or another look on someone’s face. But when biologists talk about expression, they typically mean the process of gene expression—when the information in a gene directs protein synthesis. Proteins are essential for virtually every process in the human body.

RNA, though less well known than its cousin DNA, is equally integral to our bodies. RNA molecules are long, usually single-stranded chains of nucleotides. (DNA molecules are also made up of nucleotides but are typically double-stranded.) There are three major types of RNA, which are all involved in protein synthesis:

• Messenger RNA (mRNA) is complementary to one of the DNA strands of a gene and carries genetic information for protein synthesis to the ribosome—the molecular complex in which proteins are made.
• Transfer RNA (tRNA) works with mRNA to make sure the right amino acids are inserted into the forming protein.
• Ribosomal RNA (rRNA), together with proteins, makes up ribosomes and functions to recognize the mRNA and tRNA that are presented to the ribosomal complex.

The intricate process of mitosis—a cell splitting into two identical daughter cells—plays a pivotal role in sustaining life. Many scientists study this process to understand what’s needed for it to progress normally and why it sometimes goes awry, such as in cancer. During their research, the scientists often create eye-catching images and videos, and we showcase some of those visuals here.

Check out our post Make Like a Cell and Split: Comparing Mitosis and Meiosis for more info on mitosis, and visit our image and video gallery for more examples of mitosis, as well as other scientific photos, illustrations, and videos.

Nerve cells, also known as neurons, carry information through our bodies using electrical impulses and chemical messengers called neurotransmitters. A nerve cell’s size and shape depend on its role and location, but nearly all nerve cells have three main parts:

• Dendrites that extend like branches and receive signals
• A cell body containing the nucleus that holds the genetic material of the cell and controls its actions
• An axon, a long structure that transmits messages

“It would be a dream come true if I could look at a cell within a tissue and have a Google Maps view to zoom in until I saw individual molecules,” says Melike Lakadamyali, Ph.D., an associate professor of physiology at the University of Pennsylvania’s Perelman School of Medicine in Philadelphia. Her lab is helping make part of that dream a reality by developing super-resolution microscopy tools that visualize cells at a near-molecular level.

Blending Physics and Biology

Science and math fascinated Dr. Lakadamyali since childhood, and she felt especially drawn to physics because she enjoyed using logic to solve problems. After graduating high school in her native country of Cyprus, she chose to study physics at the University of Texas, Austin. She never gave much thought to applying physics methods to biological
questions—a field known as biophysics—until her third year as an undergraduate, when she gained her first research experience in the lab of Josef Käs, Ph.D.

“A confusing experimental result almost always means you’ve stumbled upon something interesting and maybe even exciting. I think that’s what makes science fun,” says Lauren Parker Jackson, Ph.D., an assistant professor of biological sciences at Vanderbilt University, Nashville, Tennessee. Check out the highlights of our interview with Dr. Jackson to learn how she became a biologist and what she studies in her lab.

Q: What sparked your interest in science?

A: I credit my high school chemistry, physics, and biology teachers with getting me interested in science. They were quirky, they were talented, they were energetic, and they weren’t afraid to push us. As a teenager, I did a lot of science fairs and quiz bowls, where two teams compete to answer academic questions. As a high school junior, I took part in the Governor’s School for the Sciences and Engineering, where I spent a month at the University of Tennessee, Knoxville, studying chemistry in a lab. That exposed me to research for the first time.

Like skin that covers and protects our bodies, membranes surround and protect cells and organelles. Membranes are semi-fluid barriers composed mainly of lipids and proteins. They provide structure; control the import and export of molecules such as ions, nutrients, and toxins; and support cellular communication.

The lipids that compose membranes are primarily phospholipids. (Cholesterol is another lipid often present in membranes that helps regulate their stiffness.) Phospholipids have hydrophilic (water-loving) “heads” and hydrophobic (water-fearing) “tails.” Within the human body, a water-loving environment, they line up so that their tails face one another and their heads point outward. In membranes, this alignment makes a bilayer barrier that is two lipid molecules deep.

For many people, the word pathway may bring to mind stepping stones in a garden or a trail through a forest. But when biologists talk about a pathway, they’re referring to a series of actions among molecules in a cell that leads to a certain product or change within that cell. Pathways maintain balance during walking, control how the eyes’ pupils respond to light, and affect skin’s reaction to changing temperature. They control our bodies’ responses to the world, and errors in them can lead to disease.

Your body is made up of trillions of cells that all originate from just one—a fertilized egg. The massive multiplication of cells after conception is possible thanks to cell division, which occurs when one cell splits into two. Cell division not only enables growth but also replaces damaged or dead cells and makes reproduction possible. There are two kinds of cell division: mitosis and meiosis.

Mitosis is shown on the left, and meiosis is shown on the right. Credit: Judith Stoffer. Click to enlarge