phospholipid

phospholipid , lipid that in its simplest form is composed of glycerol bonded to two fatty acids and a phosphate group. The resulting compound called phosphatidic acid contains a region (the fatty acid component) that is fat-soluble along with a region (the charged phosphate group) that is water-soluble. Most phospholipids also have an additional chemical group bound to the phosphate. For example, it may be connected with choline; the resulting phospholipid is called phosphatidylcholine, or lecithin. Other phospholipids include phosphatidylglycerol, phosphatidylinositol, phosphatidylserine, and phosphatidylethanolamine. The bipolar character of phospholipids is essential to their biological function in cell membranes. The fat-soluble portions associate with the fat-soluble portions of other phospholipids while the water-soluble regions remain exposed to the surrounding solvent. The phospholipids of the cell membrane form into a sheet two molecules thick with the fat-soluble portions inside shielded on both sides by the water-soluble portions. This stable structure provides the cell membrane with its integrity.

phospholipid A polar lipid that is a lipid derivative of glycerol which contains one or more phosphate groups. Phospholipids are particularly important with regard to the structure and functioning of biological membranes because of their amphipathic qualities.

phospholipid A polar (see POLAR MOLECULE) lipid that consists of a lipid derivative of glycerol containing 1 or more phosphate groups. Phospholipids are particularly important in the structure and functioning of biological membranes.