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Food Lipids: Chemistry, Nutrition, and Biotechnology

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Figure 25 Cardiolipin structure <strong>and</strong> nomenclature.<br />

Cardiolipin is a phosphoglyceride that is present in heart muscle mitochondria<br />

<strong>and</strong> bacterial membranes. Its structure <strong>and</strong> nomenclature are shown in Figure 25.<br />

Some cardiolipins contain the maximum possible number of 18:2�6 molecules (4<br />

mol/mol).<br />

F. Ether(phospho)glycerides (Plasmalogens)<br />

Plasmalogens are formed when a vinyl (1-alkenyl) ether bond is found in a phospholipid<br />

or acylglycerol. The 1-alkenyl-2,3-diacylglycerols are termed neutral plasmalogens.<br />

A 2-acyl-1-(1-alkenyl)-sn-glycerophosphocholine is named a plasmalogen<br />

or plasmenylcholine. The related 1-alkyl compound is named plasmanylcholine.<br />

G. Glyceroglycolipids (Glycosylglycolipids)<br />

The glyceroglycolipids or glycolipids are formed when a 1,2-diacyl-sn-3-glycerol is<br />

linked via the sn-3 position to a carbohydrate molecule. The carbohydrate is usually<br />

a mono- or a disaccharide, less commonly a tri- or tetrasaccharide. Galactose is the<br />

most common carbohydrate molecule in plant glyceroglycolipids.<br />

Structures <strong>and</strong> nomenclature for some glyceroglycolipids are shown in Figure<br />

26. The names monogalactosyldiacylglycerol (MGDG) <strong>and</strong> digalactosyldiacylglycerol<br />

(DGDG) are used in common nomenclature. The st<strong>and</strong>ard nomenclature identifies<br />

the ring structure <strong>and</strong> bonding of the carbohydrate groups (Fig. 26).<br />

H. Sphingolipids<br />

The glycosphingolipids are a class of lipids containing a long chain base, fatty acids,<br />

<strong>and</strong> various other compounds, such as phosphate <strong>and</strong> monosaccharides. The base is<br />

commonly sphingosine, although more than 50 bases have been identified. The ceramides<br />

are composed of sphingosine <strong>and</strong> a fatty acid (Fig. 27). Sphingomyelin is<br />

one example of a sphingophospholipid. It is a ceramide with a phosphocholine group<br />

connected to the primary hydroxyl of sphingosine. The ceramides can also be attached<br />

to carbohydrate molecules (sphingoglycolipids or cerebrosides) via the primary<br />

hydroxyl group of sphingosine. Gangliosides are complex cerebrosides with<br />

the ceramide residue connected to a carbohydrate containing glucose-galactosamine-<br />

N-acetylneuraminic acid. These lipids are important in cell membranes <strong>and</strong> the brain,<br />

<strong>and</strong> they act as antigenic sites on cell surfaces. Nomenclature <strong>and</strong> structures of some<br />

cerebrosides are shown in Figure 27.<br />

Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved.

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