Phosphoglyserides

         All cell are surrounded by a membrane which controls the exchange of chemicals, such as food and waste products, between the cell and its environment.  Membranes are also present within cells, where they surround the various internal compartments. The major lipid component of these cell  membranes is phosphoglyserides.

         Phosphoglyserides contain a charged phosphate group and so are often referrd to as polar lipids. Propane-1,2,3-triol forms the backbone of a phosphoglyseride molecule, and two long-chain fatty acids are attached to C-1 and C-2 of the propane-1,2,3-triol  backbone by ester links. The third position is occupied by a substituted phosphate group, attached by an ester link. This phosphate group is attached, also via  an ester link, to the -OH group of a small polar molecule.

         In summary a phosphoglyseride molecule consists of:

·         a polar region or “head”, formed from the phosphate group and the attached polar molecule;

·         a non-polar “tail”, formed by the two long-chain fatty acids.

         The two non-polar long-chain fatty groups of a phosphoglyseride interact together through van der Waals’ forces and lie in the same direction. The polar phosphate group points in the opposite direction.