<prompt> Platelet-activating factor is biochemically aProstaglandinGlycolipidGlycerol ether phospholipidLeukotrienes  <response>: Platelet-activating factor PAF I-alkyl-2-acetyl-sn-glycerol-3- phosphocholine is synthesized from the corresponding 3-phosphocholine derivatives. It is formed by many blood cells and other tissues and aggregates platelets at concentrations as low as 10 molL. 