A family of compounds that includes triglycerides (fats and oils), phospholipids and sterols

Lipids are also known as fats, but they include compounds of many different kinds. Chemically, these compounds are built on a backbone of glycerol, which was a three-carbon chain. Each carbon, in turn, bonds via an oxygen molecule to so-called fatty acids. Fatty acids have an acid group (COOH) at one end that is attached to a chain of carbons. Lipids differ mainly in the nature of the fatty acid chains.

a group of fats stored in the body and used for energy

Certain lipids form an essential part of the membranes that enclose and protect every living cell. Similar membranes surround all bodies with the cell, so that each cell body can do its job without unwanted interference from other cell bodies. Lipids are also valuable as solvents (dissolving substances) for Vitamins A, d, E, and K, which do not dissolve in water.