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.
Dr. Akhila Rajan. Credit: Fred Hutchinson Cancer Research Center.
“What makes being a scientist exciting is that I don’t know what I’m going to find tomorrow,” says Akhila Rajan, Ph.D., an assistant professor in the basic sciences division at Fred Hutchinson Cancer Research Center in Seattle, Washington. Dr. Rajan is supported by an NIGMS early stage investigator Maximizing Investigators’ Research Award. These awards provide stable and flexible funding for a program of research that falls within NIGMS’ mission. Check out the highlights of our interview with Dr. Rajan to learn about her research and journey as a scientist.
It’s the spookiest time of the year! To celebrate Halloween, we’re showcasing scientific images that capture the spirit of the holiday, from a brain shaped like a bat to protein “cobwebs” in a quail embryo. Check out our image and video gallery for even more scientific photos, illustrations, and videos.
Formation of a biofilm often involves a process called quorum sensing. In this process, microbes detect when they reach a certain population density and change their behavior in ways that help them function as a community.
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
Most cells are naturally colorless, which is why scientists often use fluorescent tags and other tools to color cell structures and make them easier to study. (Check out the Pathways imaging issue for more on scientific imaging techniques). Here, we’re showcasing cell images that feature shades of blue. Visit our Image and Video Gallery for additional images of cells in all the colors of the rainbow, as well as other scientific photos, illustrations, and videos.
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.
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).
“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.