Science Snippet: The Marvels of Membranes

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. A cross section of a cell with its membrane and adjacent cell membranes outlined in gray. The colorful structures are organelles with membranes. Credit: Judith Stoffer. 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. A section of a cell membrane showing phospholipids (gold) in a bilayer formation, a membrane protein (large, green oval), and a glycan (orange chain of spheres). Credit: NIGMS. Although many small molecules and gases can pass freely across the lipid bilayer, tunnel-like proteins of the membrane must transport large or charged molecules. Along with importing and exporting nutrients and toxins, these transmembrane proteins are tasked with an important role of pumping ions into or out of the cell. The transfer resu...
Source: Biomedical Beat Blog - National Institute of General Medical Sciences - Category: Research Authors: Tags: Cells Cellular Processes Science Snippet Source Type: blogs