Apoptosis is the process by which cells in the body die in a controlled and predictable way because they have DNA damage or are no longer needed. The term comes from a Greek word meaning “falling off,” as in leaves falling from a tree.
When a cell undergoes apoptosis, it shrinks and pulls away from its neighbors. As the cytoskeleton that gives it shape and structure collapses, the envelope around the cell’s nucleus breaks down, and its DNA breaks into pieces. Its surface changes, signaling its death to other cells and leading a healthy cell to engulf the dying one and recycle its components.
Two cells in a healthy state (left) and entering apoptosis (right). Credit: Hogan Tang of the Denise Montell Lab, Johns Hopkins School of Medicine.
Credit: Jasmin Imran Alsous and Jonathan Jackson, Martin Lab, Massachusetts Institute of Technology.
What looks like a bubbling lava lamp is actually part of an egg cell’s maturation process. In many animals, the egg cell develops alongside sister cells. These sister cells are called nurse cells in the fruit fly (Drosophila melanogaster), and their job is to “nurse” an immature egg cell, or oocyte. Toward the end of oocyte development, the nurse cells transfer all their contents into the oocyte in a process called nurse cell dumping. This video captures this transfer, showing significant shape changes on the part of the nurse cells (blue), which are powered by wavelike activity of the protein myosin (red).
Proteins (such as hemoglobin, actin, and amylase) are workhorse molecules that contribute to virtually every activity in the body. Some of proteins’ many jobs include carrying oxygen from your lungs to the rest of your body (hemoglobin), allowing your muscles to move (actin and myosin), and digesting your food (amylase, pepsin, and lactase). All proteins are made up of chains of amino acids that fold into specific 3D structures, and each protein’s structure allows it to perform its distinct job. Proteins that are misfolded or misshapen can cause diseases such as Parkinson’s or cataracts.
While it’s straightforward to use the genetic code to predict amino acid sequences of proteins from gene sequences, the vast diversity of protein shapes and many factors that influence a protein’s 3D structure make it much more complicated to create simple folding rules that could be used to predict proteins’ structures from these sequences. Scientists have worked on this problem for nearly 50 years, and NIGMS has supported many of their efforts, including the Critical Assessment of Structure Prediction (CASP) program.
Dr. Hong Liu in the lab. Credit: Courtesy of Dr. Hong Liu.
“A scientific career is really worth it,” says Hong Liu, Ph.D., an assistant professor of biochemistry and molecular biology at Tulane University School of Medicine in New Orleans, Louisiana. Check out the highlights of our interview with Dr. Liu below to learn about his journey as a scientist and his advice for students.
Q: What makes a career in science exciting?
A: I think there are at least two things that make a science career very exciting. The first is that doing science means you have freedom to explore a lot of new ideas. The second thing is it’s rewarding. The “rewarding” I’m talking about here is not like how much money you can make. It’s rewarding in the answers you find and the new knowledge you reveal.
Have you ever wondered what creates striking images of cells and other tiny structures? Most often, the answer is microscopes. Many of us have encountered basic light microscopes in science classes, but those are just one of many types that scientists use. Check out the slideshow to see images researchers have captured using different kinds of microscopes. For even more images of the microscopic world, visit the NIGMS Image and Video Gallery.
Visualizing Structures
Type of Microscope: Light (Bright) field Used to Study: Living and dead cells
An immature seed of the Arabidopsis plant. The blue spot is a cell that will give rise to the endosperm, the tissue that nourishes the embryo.
Credit: Robert Fischer, University of California, Berkeley.
Type of Microscope: Dark field Used to Study: Living and dead cells
Anthrax bacteria being killed by an agent that naturally glows blue when excited by ultraviolet light in the microscope.
Credit: Keiler Lab, Penn State University.
Type of Microscope: Time lapse Used to Study: Living cells as they move over time
A dividing cell of an African globe lily. This is one frame of a time-lapse sequence that shows cell division in progress.
Credit: Andrew S. Bajer, University of Oregon, Eugene.
Type of Microscope: Super resolution light Used to Study: Activity in living cells
DNA (blue) being pulled apart by microtubules (red) as a cell divides. The blue and red colors are due to the fluorescent label used to dye the sample.
Credit: Jane Stout and Claire Walczak, Indiana University.
Type of Microscope: Fluorescent light Used to Study: Activity in dyed cells and molecules
Kidney tissue stained with fluorescent dyes that glow under high intensity light from the microscope.
Credit: Tom Deerinck and Mark Ellisman, NCMIR.
Type of Microscope: Confocal Used to Study: 3D images of living cells
Cell-like compartments that spontaneously emerge from scrambled frog eggs, with nuclei (blue) from frog sperm.
Credit: Xianrui Cheng, Stanford University School of Medicine. Xianrui Cheng, James E. Ferrell Jr. SCIENCE 366: 631, 01 Nov 2019 (DOI: 10.1126/science.aav7793).
Type of Microscope: Electron Used to Study: Dead cells
Cross-section through the worm, C. elegans, revealing various internal structures frozen in time. This image was taken with transmission electron microscopy and labeled afterwards with color to highlight features in the image.
Credit: Piali Sengupta, Brandeis University.
Type of Microscope: Cryo-EM Used to Study: Cellular components, particles (viruses, molecules, ribosomes)
The protein shell, or capsid, that surrounds HIV and is covered in a host protein (red), which allows the virus to evade detection.
Credit: Juan R. Perilla, Klaus Schulten, and the Theoretical and Computational Biophysics Group.
Students, teachers, and other curious minds can step into a scientific imaging lab with a free online interactive developed by NIGMS and Scholastic. Imaging tools help scientists unlock the mysteries of our cells and molecules. A better understanding of this tiny world can help researchers learn about the body’s normal and abnormal processes and lead to more effective, targeted treatments for illnesses.
Josephine (Josie) Chandler, Ph.D., first became interested in science when she took a high school chemistry class. In college, she fell in love with microbiology and ultimately earned a Ph.D. in the field. Today, she’s an associate professor of molecular biosciences at the University of Kansas in Lawrence, where her lab investigates interactions in bacterial communities. By better understanding these interactions, scientists may find new ways to stop infections or break down environmental pollutants—a process known as bioremediation.
Did you know that the lack of a single enzyme is responsible for lactose intolerance, a common condition that causes people to have trouble digesting milk? Fortunately, the enzyme is available in an over-the-counter pill for lactose-intolerant people who want to enjoy dairy products. Enzymes are molecules—almost always proteins—that speed up chemical reactions by reducing the amount of energy needed for the reactions to proceed. Without them, many processes in our bodies would essentially grind to a halt.
“If you bring a public health program to people where they live, you can get amazing results,” says Peter Katzmarzyk, Ph.D., a professor of pediatric obesity and diabetes at Pennington Biomedical Research Center, Louisiana State University. Specifically, bringing health programs into underserved communities can lead to strong engagement and positive changes in people’s health. Dr. Katzmarzyk is part of the NIGMS-funded Louisiana Clinical & Translational Science Center (LA CaTS), a collaboration between 10 academic, research, and health care delivery institutions that focuses on reducing health disparities in Louisiana.
Genes are segments of DNA. They contain instructions for building one or more molecules that help the body work. Researchers in the field of genetics study genes and heredity—how certain traits are passed from parents to their offspring through DNA. NIGMS supports many scientists who investigate the genetics of people and research organisms to better understand human health and disease.
Take our quiz below to test how much you know about genetics. Then check out our new fact sheet on genetics to learn more. For more quizzes and other fun learning tools, visit our activities and multimedia webpage.
