Lipids: Classification and Biological Functions

LIPIDS

Introduction

Lipids are naturally occurring organic compounds that are insoluble in water but soluble in non-polar solvents like ether, chloroform or benzene. Examples include fats, oils, waxes, sterols and fat soluble vitamins.

1. Classification of lipids:

Simple lipids:

Simple lipids are the esters of fatty acids. Example: triglycerides and waxes.

Compound lipids:

Compound lipids are esters of fatty acids with additional groups such as phosphates. Example: phosphoglycerides and phosphoinositides

Derived lipids:

The hydrolysis products of simple and compound lipids are called derived lipids.

For example hydrolysis of triglycerides yields glycerol and fatty acid.

Similarly steroids, fatty aldehydes, ketones, alcohols, fat-soluble vitamins can also be derived from the hydrolysis of simple/compounds lipids.

2. Biological Functions of lipids:

·     Lipids are important components of the cell membrane and are necessary for the structural integrity of the cell.

·     They serve as energy reserve of the body.

·     They act as a protective coating in aquatic organisms.

·     Lipids serve as insulating material on the surface of animals living in extreme cold regions.

·     They serve as component of cell recognition, species specificity and tissue immunity.

·     They help in the absorption and transport of fat soluble vitamins.