Glycerophospholipide

Glycerophospholipids are a class of phospholipids that form a major component of cellular membranes. They consist of a glycerol backbone with two fatty acids esterified at the sn-1 and sn-2 positions and a phosphate-containing head group attached at the sn-3 position. Most glycerophospholipids are diacylglycerophospholipids, but ether-linked variants exist (plasmalogens) as well.

Common head groups give rise to several well-known molecules, including phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine (PS), phosphatidylinositol (PI), and phosphatidylglycerol (PG). Cardiolipin is a unique dimeric phospholipid derived from two phosphatidic acid units and enriched in mitochondrial membranes.

Functions of glycerophospholipids include providing structural integrity to membranes, influencing fluidity and curvature, and serving as reservoirs for signaling molecules. Phosphoinositides derived from PI regulate many signaling pathways; PS externalization is involved in apoptosis; and various phospholipases release fatty acids and lysophospholipids that participate in signaling and inflammatory responses.

Biosynthesis and turnover occur via acylation of glycerol-3-phosphate and subsequent attachment of head groups through CDP-activated intermediates, followed by remodeling of acyl chains in the Lands cycle. Phospholipases hydrolyze glycerophospholipids to yield free fatty acids, lysophospholipids, and other signaling mediators.

Abnormal glycerophospholipid composition is associated with metabolic, cardiovascular, and neurodegenerative diseases. They are used in research and biotechnology, including liposome formulation for drug delivery and as biomarkers in various diagnostics.