The structures are stabilized by van der Waals interactions between the hydrocarbon chains of the nonpolar tails and interactions of the polar head groups with water. In this form they can form monolayers at the air-water interface or micelles in water. A major storage form of energy are the triacylglycerols , which are triesters of glycerol and fatty acids. Animal fats and vegetable oils are triacylglycerols and different in their content of unsaturated fatty acids. The hydrophobic core of a soap micelle can solubilize greasy dirt.
Waxes are esters of fatty acids and long chain alcohols.
All biological membranes contain lipids as the major constituent. The phosphate group is esterified to another alcohol, such as, choline, ethanolamine, etc, to produce the different phospholipids. Both sphingolipids and glycosphingolipids are fatty acyl derivatives of the long-chain amino alcohol sphingosine called ceramide. In sphingomyelin, a sphingolipid, the ceramide is esterified to phosphocholine. In glycosphingolipids, ceramide is attached to one or several saccharide head groups.