Biological Membranes

A cell membrane (also known as the plasma membrane or plasmalemma) is a biological membrane that separates the cell contents from the outside environment. A cell membrane is composed of a phospholipid bilayer and proteins that function to protect cellular DNA and mediate the exchange of ions and molecules. Additionally, the cell membrane allows the cell to communicate with other cells and also helps in tissue formation. Membranes are formed when glycerophospholipids and sphingolipids interact and expose their polar heads to the aqueous extracellular environment while sequestering their nonpolar tails toward the middle of the membrane. Proteins that are anchored in the membrane are responsible for cell signaling and interactions, transmembrane transport of substances, and for providing cellular structure.