Lipids are organic compounds which are insoluble in water, but soluble in organic solvents. They include substances like butter, ghee, vegetable oils, some plant pigments such as carotene and lycopene etc. They can dissolve in chloroform, benzene and ether.
Lipids: three categories-simple, compounds and derived.
Simple lipids are lipids formed of fatty acids and alcohol without any additional group.
Example: fats or true fats, wax, cutin, suberin etc.
Compound lipids contains group in addition to fatty acid and alcohol.
Example: phospholipids, sphingomyelins, glycolipids, sulpho lipids, lipoprotein etc.
Derived lipids are derivatives of lipids
Example: Steroids and sterol like cholesterol, lipid soluble vitamins, lipid soluble hormones, terpenes, prostaglandin etc.
Different types of lipids:
Triglycerides: They are esters of fatty acids and 3 carbon trihydric alcohol glycerol. Being trihydric, glycerol forms ester linkages with three fatty acid molecules. True fat is also called triglycerides.
Waxes are chemically inert esters of long chain fatty acids with monohydric higher alcohol.
Cutin: It is a lipid formed by polymerization and cross esterification of hydroxyl fatty acids.
Suberin: It is a lipid formed by esterification of phellonic acid or its derivatives with glycerol.
Phospholipid: They are compound lipids or phosphoglycerides where the third hydroxyl group of glycerol is esterified to phosphoric acid making it strong polar head.
Sphinogomyelins: The lipids do not contain glycerol. Instead a complex amino alcohol sphingosine is found.
Glycolipids: They are lipids having sugar residues.
Terpenoids or Terpenes: They are a large group of lipids that are formed by repeating units called isoprene.
Prostaglandins: It is a group of hormone like derivatives of unsaturated fatty acids. They are derived from arachidonic and related C20 fatty acids.