Lipids

Classification of Lipids

Lipids that are ester or amides of fatty acids:

Waxes – are carboxylic acid esters where both

R groups are long straight hydrocarbon chain.

Performs external protective functions.

Triacylglycerol – are carboxylic acid triesters of glycerols. They are a major source of

biochemical energy.

Glycerophopholipids - triesters of glycerols that contain charged phosphate diesters. They help to control the flow of molecules into and out of cells.

Sphingomyelins – amides derived from an

amino alcohol, also contain charged

phosphate diester groups. They are essential

to the structure of cell membranes.

Glycolipids – amides derived from

sphingosine, contain polar carbohydrate

groups. On the cell surface, they connect with

by intracellular messengers.

Lipids that are not esters or amides:

Steroids – They perform various functions such as hormones and contributes to the structure of cell membranes.

Eicosanoids – They are carboxylic acids that are a special type of intracellular chemical messengers.

24.3 Properties of Fats and Oils

Oils: A mixture of triglycerols that is liquid

because it contains a high proportions of

unsaturated fatty acids.

Fats: A mixture of triglycerols that is solid

because it contains a high proportions of

saturated fatty acids.

Properties of triglycerols in natural fats and

oils:

Nonpolar and hydrophobic

No ionic charges

Solid triglycerols (Fats) - high proportions of

saturated fatty acids.

Liquid triglycerols (Oils) - high proportions

of unsaturated fatty acids.

Chemical Reactions of Triglycerols

Hydrogenation: The carbon-carbon double bonds in unsaturated fatty acids can be hydrogenated by reacting with hydrogen to produce saturated fatty acids. For example, margarine is produced when two thirds of the double bonds present in vegetable oil is hydrogenated.

Hydrolysis of triglycerols: Triglycerols like any

other esters react with water to form their carboxylic acid and...