Structure and Biological Significance of Lipids

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Structure and Biological Significance of Lipids

Lipids are made up of a wide variety of molecules, but they all

contain carbon, hydrogen and oxygen, with a much higher percentage of

carbon and hydrogen molecules than oxygen.

There are three kinds of lipids in living organisms: triglycerides,

phospholipids and steroids (hormones).

Triglycerides are made up of a glycerol molecule, with three fatty

acid chains attached by ester linkages. Glycerol is an alcohol

containing 3 carbon atoms. The fact it is an alcohol means it has an

-OH group at one end. Fatty acids are hydrocarbon chains, with a -COOH

group at one end. This -COOH group reacts with the -OH group of

glycerol, and a condensation reaction occurs, which is what forms the

ester linkage. As this breaks apart the -COOH group, which is what

makes fatty acids acidic, once the condensation reaction has occurred,

the fatty acids will no longer have any acidic properties.

As the triglyceride is effectively surrounded by hydrocarbons, it is

hydrophobic (water-ha...

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