Every cell and organelle in the human body is encapsulated by a biological membrane composed of orderly lipid molecules called phospholipids. Biological membranes maintain the architecture and physiology of cells and organelles and serve as the initiation point for critical intracellular signaling pathways. THE COMPOSITION OF BIOLOGICAL MEMBRANES Biological membranes are composed primarily of phospholipids. Phospholipids create a barrier to the passage of molecules and ions in and out of cells, allowing cells to carefully monitor their environment. The predominant phospholipid in biological membranes is phosphatidylcholine. Unsaturated fatty acids, such as alpha-linolenic acid (ALA), are interspersed within the phospholipid bilayer, lending fluidity to cell membranes. Carotenoids and vitamin E molecules, including the tocopherols and tocotrienols, nestle inside biological membranes, acting as sentinels that rapidly address oxidative threats to the membrane.
