Lipids that are composed of fatty acids, glycerol and phosphate are called phospholipids. Its constituents are phosphotidic acid. Lecithin when the phosphate group of phospholipid is esterified with choline and serine when esterified with hydroxyl gives cephalin. Lecithin was the first phospholipid identified. Phospholipid holo-lecithin, cephalin, plasmalogen, choline, serine, cardiolipin, sphingomyolin etc.
Phospholipids are of three types. These are-
(i) Phosphoglycerides: Phospholipids composed of glycerol, fatty acids and phosphoric acid are called phosphoglycerides. It is present in the cell membrane. Such as lecithin. Dr. Siddiq Publications
(ii) Phosphoinositide: Phospholipids composed of glycerol, fatty acids, phosphoric acid and inositol are called phosphoinositides. It is present in the brain. It is found in soybeans.
(iii) Phosphosphingoside: Phospholipids composed of fatty acids, phosphoric acid and sphingosine are called phosphosphingosides. It resides in the nervous system of animals.
Functions of phospholipids
(i) Phospholipid forms the membrane of cell mitochondria, chloroplast, tonoplast, endoplasmic reticulum, nucleus etc.
(ii) It regulates cell permeability and transport processes.
(iii) Acts as a prosthetic group in some enzymes.
(iv) It helps in coagulation or coagulation of blood in the animal body.
(v) It acts as cell ion. Blocks diffusion of glucose, water and charged ions.
(vi) It increases the rate of oxidation.
(vii) It plays an important role in acetylcholine neurotransmission.
(viii) It helps in jasmonic acid production in plant cells. Jasmonic acid participates in disease prevention.
(ix) It maintains the internal stability of the cell.