We couldn’t survive without proteins. They’re essential molecules that provide cells with structure, aid in chemical reactions, support communication, and much more. Portion out protein numbers with us below!

10 Trillion

That’s how many proteins scientists estimate are in each human cell.

229,378

That’s how many structures researchers shared with the scientific community through the Protein Data Bank (PDB) from its establishment in 1971 to the end of 2024. The PDB is a global repository for 3D structural data of proteins, DNA, RNA, and even complexes these biological molecules form with medicines or other small molecules.

42

That’s the percent of your body weight (not counting water) that’s made up of proteins.

Cells rely on garbage and recycling systems to keep their interiors neat and tidy. If it weren't for these systems, cells could look like microscopic junkyards—and worse, they might not function properly. So constant cleaning is a crucial biological process, and if it goes wrong, accumulated trash can cause serious problems.

Proteasomes: Cellular Garbage Disposals

One of the cell's trash processors is called the proteasome. It breaks down proteins, the building blocks and mini-machines that make up many cell parts. The barrel-shaped proteasome disassembles damaged or unwanted proteins, breaking them into bits that the cell can reuse to make new proteins. In this way, the proteasome is just as much a recycling plant as it is a garbage disposal.

“Curiosity was a central theme in my learning process,” says Sudha Chakrapani, Ph.D., a professor and chair of the department of pharmacology at Case Western Reserve University in Cleveland, Ohio. As a high schooler in India, she especially enjoyed her science classes because they fostered her curiosity and allowed her to ask more questions than other subjects did. She was curious about how to use science to solve the challenges she and her community faced, like access to safe drinking water. Seawater surrounded them, so could they find a way to convert it into drinking water?

As part of India’s annual National Teachers’ Day celebration, high school seniors take on the role of educators and teach their younger peers for the day. Dr. Chakrapani loved the experience, and it solidified what she already knew: She wanted to go to college to be a science teacher. After earning her bachelor’s degree, she entered back-to-back master’s programs in biochemistry and biomedical engineering, where she had the opportunity to do hands-on research.

“I think it’s really an exciting time for science. Some people might think that everything out there to be discovered has already been discovered, but that’s far from the truth. There is still much, much more to discover,” says John Jimah, Ph.D., an assistant professor of molecular biology at Princeton University in Princeton, New Jersey. We talked with him about how he moved internationally to pursue his career, how his current research on cell membranes could help treat malaria, and how science holds space for everyone.

“Throughout my career, I’ve enjoyed studying topics that no one else seems to care about. I always tell people that I like searching through the scientific garbage bin for inspiration,” says Ahna Skop, Ph.D., a professor of genetics at the University of Wisconsin-Madison. We talked with her about the backyard experiment that helped her gain confidence in her scientific abilities, her career-long pursuit to better understand a detail about cell division that others had written off as unimportant, and her desire to build an accessible scientific community.

Q: How did you first become interested in science?

A: Middle school and high school science fairs had a big impact on me. I would develop my ideas, and with the help of my dad, build the experimental setup I needed to answer the scientific question. One of my experiments studied whether ants preferred to eat salt or sugar, so I poured small piles of both all over the backyard and took daily measurements of the height of the piles to figure out which type was shrinking faster. (Spoiler alert for those of you who might try this at home: They liked both but preferred the sugar to the salt.)

“I remember thinking in my first cellular biology class how impossibly beautiful it is that there are tiny machines in our bodies doing work,” says Morgan DeSantis, Ph.D., an assistant professor of molecular, cellular, and developmental biology at the University of Michigan in Ann Arbor. We talked with Dr. DeSantis about how her career in science almost didn’t happen, how happy she is that it did, and what she’s learning through her research on molecular machines.

Q: How did you become interested in science?

A: I wasn’t remotely interested in science in high school—I was a self-identified artist. I went to the College of Wooster in Ohio with the sole purpose of studying art and doing pottery. But one day during my freshman year, a box with all the pieces I made throughout the year fell, and everything inside broke. It’s hard to describe the emotions I felt that day, but something changed in me, and I realized pottery wasn’t for me. I couldn’t start the projects over, and I didn’t want to drop out and move back home. So, I decided to become a medical doctor.

Happy Valentine's Day! In place of red roses, we hope you'll accept a bouquet of beautiful scientific images featuring rich, red hues. Be sure to click all the way through to see the festive protein flowing through your blood!

For more scientific photos, illustrations, and videos in all the colors of the rainbow, visit our image and video gallery.

This August marks 10 years of the blog! Throughout the past decade, we’ve brought you blog posts that explore basic science topics, quiz your knowledge, showcase cool images, and more! Some of our most-read favorites include:

Copper pipes, copper wires, copper…food? Copper is not only a useful metal for conducting electricity, but it’s also an essential element we need in our bodies for a variety of important activities—from metabolizing iron to pigmenting skin.

Copper is required to keep your body going. Enzymes that use copper are called cuproenzymes, and they catalyze a wide range of reactions, including making neurotransmitters and connective tissue. The element is found on the Statue of Liberty’s covering, in wiring and electronics, and in the blue blood of crustaceans. Credit: Compound Interest CC BY-NC-ND 4.0. Click to enlarge.