Triacylglycerols mixed

Stearoyl, 2-linoleoyl, 3-palmitoyl glycerol, a mixed triacylglycerol... 

FIGURE 10-2 Glycerol and a triacylglycerol. The mixed triacylglycerol shown here has three different fatty acids attached to the glycerol backbone. When glycerol has two different fatty acids at C-1 and C-3, the C-2 is a chiral center (p. 76). 

Fig. 1. Structure of (a) a simple triacylglycerol (1,2,3-tripalmitoyl-glycerol) and (b) a mixed triacylglycerol (1 -palmitoyl-2,3-dioleoyl-glycerol).

Simple triacylglycerols are composed of three identical fatty acid side chains, whereas mixed triacylglycerols have two or three different fatty acids. Table 29.2 lists the most common fatty acids used to form triacylglycerols. 

Triacylglycerols contain three fatty acid molecules esterified to the three hydroxyl groups of glycerol. Simple triacylglycerols contain only one type of fatty acid mixed triacylglycerols, two or three types. Triacylglycerols are primarily storage fats they are present in many foods. 

Triacylglycerols can be simple triacylglycerols in which all three acyl groups are the same. More commonly, however, the triacylglycerol is a mixed triacylglycerol in which the acyl groups are different. 

Lipases a group of carboxylesterases, which preferentially hydrolyse emulsifi neutral fats to fatty acids and glycerol or monoacylglycerols. Calcium ions are required for activity. Pancreatic L. also requires taurocholate. Pancreas and certain plant seeds (e.g. Ricinus) contain particularly high activities of L.In addition, high activities are found in adipose tissue, in the stomach (especially in unweaned infants) and in the liver. Pancreatic L. has M, 35,000. Rapid removal of the third and last fatty acid residue from mixed triacylglycerols is catalysed by a specific mono-acylglycerol lipase (EC 3.1.1.23) produced by the intestinal mucosa. 

Triacylglycerols differ in type according to the nature and position of the fatty acid residues. Those with three residues of the same fatty acid are termed simple triacylglycerols, as illustrated above. When more than one fatty acid is concerned in the esterification, a mixed triacylglycerol results ... 

Ri, R2 and R3 represent the chains of different fatty acids. Naturally occurring fats and oils are mixtures of such mixed triacylglycerols. Soya bean oil has been estimated to contain about 79 per cent of mixed triacylglycerols compared with about 21 per cent of the simple type. Comparable figures for linseed oil are 75 and 25 per cent, respectively. Triacylglycerols with residues of one fatty acid only do occur naturally laurel oil, for example, contains about 31 per cent of the triacylglycerol of lauric acid. 

EI-MS with direct probe insertion was used, for example, to determine the structure of unusual tetraacylglycerols containing an allenic acid [877] and triacylglycerols containing sorbic acid [251]. Molecular species of mixed triacylglycerols have also... 

Three different fatty acids can occur from 27 different mixed triglycerides. To simplify the description, one- or two-letter abbreviations of fatty acids are used, such as B = butanoic (butyric), D = decanoic (capric or caprinic), H = hexanoic (caproic), L = linoleic, La = lauric, Ln = linolenic, M = myristic, O = oleic, Oc = octanoic (caprylic), P = palmitic, Po = palmitoleic, S = saturated, St = stearic, U = unsaturated and V = vaccenic. For example, the mixed triacylglycerol esterified with palmitic acid in position s -l, with stearic acid in the position sn-2 and oleic acid in the position sn-3 of glycerol is then called l-palmitoyl-2-stearoyl-3-oleoyl-s -glycerol (abbreviated to s -PStO). Racemate is a mixture of s -PStO and and s -OStP in a molar ratio of 1 1... 

Most naturally occurring triacylglycerols contain glycerol bonded to two or three different fatty acids, typically palmitic acid, oleic acid, linoleic acid, and stearic acid. For example, a mixed triacylglycerol might be made from stearic acid, oleic add, and palmitic acid. One possible structure for this mixed triacylglycerol follows ... 

Draw the condensed structural formula for a mixed triacylglycerol that contains two palmitic acid molecules and one oleic acid molecule on the second carbon (center carbon) of glycerol. 

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