What Makes Up Lipids?

All lipids contain carbon, hydrogen, and oxygen. Some of them also contain nitrogen and phosphorus. The four main classes of lipids are fats, waxes, sterols, and phospholipids. Fats Fats are triglycerides. They are triesters formed by the reaction of glycerol and any of several fatty acids. Fats may be either solid or liquid at room temperature, depending on their structure and composition. Fats that are liquids at normal room temperature are usually called oils. Fats that are solids at normal room temperature are usually called fats. Waxes Waxes are organic compounds that usually consist of long hydrocarbon chains. Many natural waxes contain esters of long-chain carboxylic acids and long-chain alcohols. Sterols Sterols are derivatives of cholesterol. They all have the basic structure Examples are cholesterol, sitosterol, and campesterol. Fats, waxes, and sterols contain only carbon, hydrogen, and oxygen. Phospholipids Most phospholipids contain a diglyceride, a phosphate group, and a simple organic molecule such as choline. Thus, they contain phosphorus and nitrogen. A typical phospholipid is phosphatidylcholine.