Fatty acid with 4 to 6 carbon atoms is called short chain fatty acids (SCFA) (e.g. Butyric acid) and those with 8 to 14 carbon atoms are called medium chain fatty acids (MCFA), (e.g. Lauric acid). MCFA digestion does not require pancreatic lipase and bile salts. They diffuse directly into the portal circulation. Deficient oxidation of VLCFA by peroxisomal oxidation leads to adrenoleukodystrophy. PUFA form membrane lipids, influence fluidity of the plasma membrane and act as precursors for prostaglandin synthesis. Cyclooxygenase is an example of a ‘suicide enzyme’. Aspirin irreversibly inhibits the enzyme. Prostaglandins act as local hormones and function through G protein coupled receptors. In most cases PGE increases cAMP. TXA2 is produced by platelets. It promotes platelet aggregation and causes vasoconstriction. Prostacyclin and Thromboxanes are opposite in their actions on cAMP. Leukotrienes LTC4, LTD4 and LTE4 constitute the slow reacting substance of anaphylaxis (SRS-A). PGF2 may be used for medical termination of pregnancy, since it stimulates uterine muscles. Compound lipids contain molecules other than fatty acid and alcohol. Sphingomyelins are the only sphingolipids, which contain phosphate and does not contain a sugar residue. Deficiency of enzymes of sphingolipid metabolism results in Sphingolipidoses, a group of inborn metabolic disorders resulting in accumulation of specific lipid residues. Mental retardation, neurological deficit and skeletal abnormalities are common presenting symptoms.