Cell membrane Structure and Function
Cell membrane (CM, plasma membrane, cytoplasmic membrane) is a biological membrane that separates interior of all cells from the outside. Basic function of CM is to protect cell from its surroundings. Cell membrane is a delicate, two-layered structure of lipids and proteins. The most widely accepted model of membrane is fluid mosaic model of S. J. Singer & G. L. Nicolson (1972). According to the Fluid mosaic model, the double layer of membrane consists of lipid layer made up of a hydrophilic (water-loving, polar) head, along with two hydrophobic (water-fearing, non-polar) tails. Lipids spontaneously arrange themselves in a double-layered structure with their hydrophobic tails pointing inward & hydrophilic heads facing outward. This energetically favourable two-layer structure, called a lipid bilayer, is found in many biological membranes.