Ester is any of an important group of organic (carbon-containing) compounds. Esters belong to a class of oily or fatty substances called lipids. Lipids occur widely in plant and animal cells. Like other lipids, esters do not dissolve in water.
Esters can form when alcohols react chemically with acids. For example, ethyl alcohol reacts with acetic acid to form the ester ethyl acetate and water.
Waxes are esters that act as a protective, waterproof coating on skin, feathers, and leaves. Esters called phosphoglycerides serve as “building blocks” of cell membranes. Fats are esters of an alcohol called glycerol and fatty acids. Much of cholesterol—a fatty alcohol found in animal tissues—reacts with fatty acids in the body to form a complex mixture of esters. Other esters give fragrance to flowers and flavor to fruits. Menthyl acetate is an ester found in peppermint oil. Esters are used to make polyesters, a group of materials that are commonly used in fabrics.
