Glycerophospholipids

Abstract Glycerophospholipids are derivatives of sn ‐glycero‐3‐phosphoric acid. They contain an O ‐acyl or O ‐alkyl or O ‐alk‐1′‐enyl residue at the sn ‐1 position and an O ‐acyl residue at the sn ‐2 position of the glycerol moiety and are defined on the basis of the substituents on the phosphoric acid at the sn ‐3 position. Glycerophospholipids are asymmetrically distributed between the two bilayers membranes, which also contain cholesterol and proteins. Glycerophospholipids not only constitute the backbone of cellular membranes, but also provide the membrane with a suitable environment, fluidity and ion permeability. They are synthesised at the endoplasmic reticulum and are transported to other membranous structures by phospholipid exchange and transfer proteins. Once glycerophospholipids are laid down in a biomembrane, they undergo interconversion reactions. These reactions and activities of phospholipases may be responsible for the turnover, compositional maintenance and rearrangements of glycerophospholipids in membranes. This process results in the modulation of membrane function. Glycerophospholipids are precursors for lipid mediators, which play important roles in internal and external communication and modulate cellular responses. In addition, glycerophospholipids and their lipid mediators may be involved in membrane fusion, apoptosis and regulation of the activities of membrane‐bound enzymes and ion channels. Key Concepts: Lipid bilayers provide the fundamental architecture of biological membranes, which are made up of lipids (phospholipids, cholesterol and sphingolipids) and proteins. The role of lipids is to provide membranes with integrity and flexibility, whereas embedded proteins in biomembrane are associated with the maintenance of cellular chemical climate. Phospholipids are reservoir for lipid mediators, cholesterol provides flexibility, and sphingolipids and cholesterol are involved in formation of lipid rafts. Lipid mediators not only transduce signals from the cell surface to the interior, but also modulate gene expression, growth, differentiation, adhesion, migration and apoptosis. Arachidonic acid‐derived lipid mediators induce oxidative stress and inflammatory effects. Docosahexaenoic acid‐derived lipid mediators produce antioxidative and anti‐inflammatory effects.