As their name suggests, the triglycerides are composed of one molecule of glycerol and joined via ester bonds with three molecules of fatty acids. As is shown in Figure 12, fatty acids are long chains of carbon and hydrogen usually between 14-24 carbons long (and they always have an even number of carbons).. Phospholipids: This class of lipids are really derivatives of triglycerides. The are composed of a glycerol molecule with two fatty acids (a diglyceride). The third carbon contains a phosphate group and usually some added polar molecule (such as ethanolamine, serine or choline).