Lipids
The lipids include a large number of biomolecules of different types. Those constituents of the cell which are insoluble in water and soluble in organic solvents of low polarity (such as chloroform, ether, benzene, etc.) are termed as lipids.
Classification of Lipids
Lipids are classified into three broad categories on the basis of their molecular structure and the hydrolysis products.
Simple Lipids
Those lipids which are esters and yield fatty acids and alcohols upon hydrolysis are called simple lipids. They include oils, fats and waxes.
Compound Lipids
Compound lipids are esters of fatty acids and alcohol with additional compounds like phosphoric acid, sugars, proteins, etc.
Derived Lipids
Compounds which are formed from oils, fats, etc. during metabolism. They include steroids and some fat soluble vitamins.