Glycerolipids

This is a diacylglycerol. Diacyl- and monoacylglycerols are found in cells, but only in small amounts they are metabolites of TAGs and phospholipids. 

Question Depot fat has a relatively high content of unsaturated fatty acids. What advantage does this have for the cell  

The fat exists in a liquid state. Solid fat would present only a small surface area for enzymes in the cytoplasmic water that mobilize it. Also, solid fat would render the adipose tissue rigid and unyielding during mechanical stress. 

Usually the melting point of depot fat is only a few degrees below body temperature. The fatty acid composition of depot fat thus is a compromise between the requirement for keeping the fat liquid and the ability to store as much energy as possible. (Unsaturated fatty acids yield less energy than saturated ones of the same size, when oxidized.) 

Phosphoglycerides are polar glycerolipids and are often referred to as phospholipids. However, some other lipids, not containing glycerol, also contain phosphorus, and the term phospholipid also describes these. The term phospholipid will be used here to describe any lipid containing phosphorus. 

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FIGURE 25.18 Synthesis of glycerolipids in eukaryotes begins with the formation of phosphatidic acid, which may be formed from dihydroxyace-tone phosphate or glycerol as shown. 

Eukaryotes Synthesize Glycerolipids from CDP-Diacylglycerol or Diacylglycerol... 

FIGURE 25.19 Diacylglycerol and CDP-diacylglycerol are the principal precursors of glycerolipids in eukaryotes. Phosphatidylethanolamine and phosphatidylcholine are formed by reaction of diacylglycerol with CDP-ethanolamine or CDP-choline, respectively. 

The enzymes in peroxisomes do not attack shorter-chain fatty acids the P-oxidation sequence ends at oc-tanoyl-CoA. Octanoyl and acetyl groups are both further oxidized in mitochondria. Another role of peroxisomal P-oxidation is to shorten the side chain of cholesterol in bile acid formation (Chapter 26). Peroxisomes also take part in the synthesis of ether glycerolipids (Chapter 24), cholesterol, and dolichol (Figure 26-2). 

Vance DE Glycerolipid biosynthesis in eukaryotes. In Biochem-istry of Lipids, Lipoproteins and Membranes. Vance DE, Vance JE (editors). Elsevier, 1996. 

Ethanol and choline glycerolipids were isolated from calf brain and beef heart lipids by PTLC using silica gel H plates. Pure ethanol amine and choline plasmalogens were obtained with a yield of 80% [74]. Four phosphohpid components in the purple membrane (Bacteriorhodopsin) of Halobacterium halobium were isolated and identified by PTLC. Separated phosphohpids were add-hydrolyzed and further analyzed by GC. Silica gel G pates were used to fractionate alkylglycerol according to the number of carbon atoms in the aliphatic moiety [24]. Sterol esters, wax esters, free sterols, and polar lipids in dogskin hpids were separated by PTLC. The fatty acid composition of each group was determined by GC. 

Glycerolipids Animal fats, vegetable oils (e.g. palm oil, olive oil) including drying oils (e.g. linseed, walnut, poppy seed) Paint binders, varnishes, illuminants, commodities, ingredients of cosmetic and pharmaceutical preparations... 

A. Andreotti, I. Bonaduce, M.P. Colombini, G. Gautier, F. Modugno, E. Ribechini, Combined GC/MS analytical procedure for the characterization of glycerolipid, waxy, resinous, and proteinaceous materials in a unique paint microsample, Analytical Chemistry, 78, 4490 4500 (2006). 

Sometimes it is possible only to assess the presence or absence of glycerolipids. 

The pyrolysis of glycerolipid materials requires the use of a suitable derivatising agent, in order to increase the detectability of fatty acids and dicarboxylic acids, which may be present in a mature paint film as free acids, metal soaps, as well as esterified with glycerol. The oils and fats commonly used in samples from works of art have been analysed by means of pyrolysis using TMAH [12,23,25,26,32 38], and HMDS [37,39]. 

Glycerolipids are derivatives of glycerol and fatty acids 34 In sphingolipids, the long-chain aminodiol sphingosine serves as the lipid backbone 37... 

Acetyl coenzyme A is the precursor of both cholesterol and fatty acids 39 Phosphatidic acid is the precursor of all glycerolipids 42 Sphingolipids are biosynthesized by adding head groups to the ceramide moiety 44... 

Hajra, A. K. Glycerolipid biosynthesis in peroxisomes (microbodies). Prog. Lipid Res. 34 343-364,1995. 

The method was first applied to the preparation of a number of simple alkyl and aryl C-l glycals,71 but since then the scope of this approach have been extended with the preparation of a small library of significant C-l glycals including steroidal, and glycerolipidic residues endowed with potential biological activity.72... 

Peptideglycan biosynthesis Metabolism of Complex Lipids Glycerolipid metabolism Inositol phosphate metabolism Sphingophospholipid biosynthesis Phospholipid degradation Sphingoglycolipid metabolism Prostaglandin and leukotriene metabolism... 

Agranofl, B. W., Hajra, A. K. The acyl dihydroxyacetone phosphate pathway for glycerolipid biosynthesis in mouse liver and Ehrlich ascites tumor cells. Proc. Natl. Acad. Sci. U.S. 68, 411-415 (1971). 

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