Cholesterol (sometimes also known as cholesterin) is the principle sterol (an ester of a fatty acid and an aromatic (ring structure) alcohol) found in all animal tissues. The name comes from the Greek chole and stereos and it means "solid bile." High levels of cholesterol have been implicated in some forms of atherosclerosis (a disease caused by the thickening of arterial walls).

Cholesterol is found in humans in both free and esterified forms. It was first isolated from humans in gallstones. Cholesterol is now commercially obtained from cattle spinal cords or from lanosterol--the fatty coating of sheep wool.

Cholesterol is manufactured by all animals from ethanoate (a salt of ethanoic acid) molecules via the intermediates mevalonic acid, squalene, and lanosterol. Cholesterol is biologically important as a constituent of the plasma membranes of many animal cells. It is also present in smaller amounts in the membranes of the mitochondria...