What are lipids? Write their main functions.

Lipids are a diverse group of naturally occurring bio-molecules that have limited solubility in water and can be isolated from organisms by extraction with non polar solvents. Lipids are defined on the basis of physical property (solubility) that is sued to isolate them.
Functions:
(1) Oils and fats store food energy in plants and animals.
(2) Waxes provide vital waterproofing for body surfaces. They are water repelling solids and form protective coatings on leaves, fruits, berries, animal fur and feathers of birds.
(3) Bile acids ( a type of steroids) help in digestion of fat in the intestine.
(4) Prostaglandins lower blood pressure, affect blood platelet aggregation during clotting, lower gastric secretion and stimulate uterine contractions during child birth.