Lipids: They are macro biomolecules. They are organic compounds; insoluble in water but soluble in organic solvents such as chloroform, benzene, and petroleum, ether, etc. They have long chains of aliphatic hydrocarbons or a benzene ring. Oil, butter, ghee, waxes, natural rubber, and cholesterol are either lipids or rich in lipids. Fats form an important structural component of cell membranes, pigments such as carotene and lycopene, menthol, hormones, and vitamins A, E and K. Chemically, fats are compounds of C, H, and O.