Campbell 3rd ed.
Lipids are a varied group of molecules most of which are insoluble in water.
Like carbohydrates, carbon, hydrogen, and oxygen are the principal elements of lipids although the oxygen content is much reduced. Fats, phospholipids, steroids, carotenoids, and waxes are lipids. Fats are the most abundant group of lipids in the biological world. Fats are composed of three fatty acid molecules bonded to a molecule of the alcohol glycerol. Fats have at least twice the energy ,storing capacity per unit weight as carbohydrates do.