![]() ![]() ![]() 8.19:Īlthough ester-linked lipids are present in most organisms, an exceptional type of lipids occurs in the membranes of archaebacteria and in some primitive eubacteria. This is diagrammatically represented in Fig. Thus, in a bilayered membrane, lipids form the middle hydrophobic layer and glycerol and protein remain on two sides facing the outer and inner aqueous environment. The same principle applies also in the formation of biological membranes in which the hydrophilic glycerol and protein molecules form a layer towards the outside and the lipid-tails remain inside. In these droplets, the lipid molecules are oriented in such a manner that the hydrophilic glycerol moieties remain in contact with water, while the fatty acid tails project inward to build a compact hydrophobic central zone. When oil or fat is dispersed in water, they form an unstable emulsion consisting of small droplets of oil or fat. It is important to note that the hydrophobic nature of fats and oils is due to the long-chain fatty- acids which are highly insoluble in water and are strongly hydrophobic, though glycerol itself is a hydrophilic compound. The structure of a triglyceride and the formation of ester- bond are shown in Fig. ![]()
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