glycerolipid

Glycerolipids are a class of lipids that share a glycerol backbone. They include neutral glycerides such as triacylglycerols (triglycerides), which function predominantly as energy storage in adipose tissue, and glycerophospholipids, the major structural lipids of cell membranes. Mono- and diacylglycerols are also considered glycerolipids and serve as intermediates in metabolism and signaling.

Structurally, glycerolipids consist of a glycerol backbone esterified at the first and second positions with fatty acids. In glycerophospholipids, the third hydroxyl is linked to a phosphate-containing head group (for example choline, ethanolamine, serine, or inositol), giving distinct membrane properties. Some glycerolipids contain ether linkages or additional modifications (plasmalogens).

Biosynthesis and metabolism: In animals, glycerol-3-phosphate is acylated to form lysophosphatidic acid and phosphatidic acid, which can be dephosphorylated to diacylglycerol. DAG serves as a precursor to triacylglycerols via DGAT or to various phospholipids by transfer of head groups. TAGs are formed by sequential acylation of DAG and are the main energy reserve, while phospholipids such as phosphatidylcholine and phosphatidylethanolamine are prominent membrane components. Signaling lipids such as DAG and certain lysophospholipids participate in cellular signaling.

Function and occurrence: Glycerolipids are essential for membrane structure, energy storage, and signaling. They are abundant in all tissues; TAGs are particularly enriched in adipose tissue, whereas phospholipids are widespread in cellular membranes and lipoproteins. Abnormal glycerolipid metabolism is linked to metabolic diseases such as obesity, diabetes, and non-alcoholic fatty liver disease.

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