Glycerol forms the backbone for the fats/oils (tricylglyerols), the glycerophospholipids, diacyglycerols, and the monoacylglycerol. Free glycerol is produced metabolically by digestion of a fat or phospholipids. It can enter the glycolytic pathway via phosphorylation (requires ATP) in the liver by the enzyme glycerol kinase to form glycerol-3-phosphate, which is then oxidized to dihdroxyacetone phosphate. Dihydroxyacetone phosphate is, of course an intermediate in other pathways, such as glycolysis, gluconeogenesis, and in phospholipid synthesis.

Free glycerol is also produced in synthesis of cardiolipin from phosphatidylglycerol (Figure 19.4)