Mammalian membrane glycolipids

C2oH35NO,5 529.494 Found in glycoproteins and membrane glycolipids of mammalian cells. Formed during embryonic development and cell differentiation. Serological determinant. Mp 140-142°. [a]o -33 (c, 1.0 in H2O). 

Retinyl phosphate has been shown to be formed in mammalian cells both in vitro and in vivo and has been identified as a trace constitutent of certain mammalian membranes. Its glycosylated derivative mannosyl retinyl phosphate has also been shown to be formed both in vivo and in vitro. The enzyme system that forms mannosyl retinyl phosphate is located primarily in the rough endoplasmic reticulum of rat liver cells. Under appropriate conditions, glycosyl transfer can be demonstrated from the retinyl glycolipid to membrane glycoproteins. It is not known, however, whether this occurs in vivo under normal conditions. 

The presence and biological importance of oligosaccharide structures, usually as components of glycolipids and glycoproteins, in bacterial capsular and cell-wall polysaccharides, in mammalian cell membranes, in cytoplasm, and in extracellular fluids, are now well documented. They are important constituents in... 

Phospholipids, glycolipids, and cholesterol are the major components of mammalian cell-membrane lipids. They... 

All mammalian cells are enclosed by a plasma membrane composed of a lipid bilayer (two layers) containing embedded proteins (Fig. 10.2). The membranes are continuous and sealed so that the hydrophobic lipid bilayer selectively restricts the exchange of polar compounds between the external fluid and the intracellular compartment. The membrane is referred to as a fluid mosaic because it consists of a mosaic of proteins and lipid molecules that can, for the most part, move laterally in the plane of the membrane. The proteins are classified as integral proteins, which span the cell membrane, or peripheral proteins, which are attached to the membrane surface through electrostatic bonds to lipids or integral proteins. Many of the proteins and lipids on the external leaflet contain covalently bound carbohydrate chains and therefore are glycoproteins and glycolipids. This layer of carbohydrate on the outer surface of the cell is called the gly cocalyx. 

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