(i) Chemical properties of Lipids: Hydrolysis: On hydrolysis with alkali or lipolytic enzyme lipases, fats are broken down into their components fatty acids and glycerols.
Saponification Value : It is the amount in mg of alkali required to saponify 1 gm of fat or oil. This value is useful for a comparative study of fatty acid chain-length in oils.
(ii) Chemical structure of lipids: Lipids are a heterogeneous group of fats or fat like substances which are insoluble in water but soluble in non-polar solvents like ether, acetone, e.g., ghee, butter, oil, vitamins A, E and K.
Lipids are formed of carbon, hydrogen and often oxygen where oxygen content is very small as compared to other two elements. Lipids require more oxygen for their complete oxidation as compared to carbohydrates. Some lipids also contain small amount of phosphorus nitrogen and rarely sulfur. Most lipids are formed of fatty acids.
Lipids are water insoluble components of the living cells and are essential for storing surplus food. They provide insulation to heat loss and protect internal organs from abrasion. Most biological membranes contain around 50-40% of lipids. Some lipids act as carrier of some vitamins (vitamin A,D, E and K) and also protect them from oxidation. In animals, the fats produce a shock absorbing cushion around eye balls, gonads, kidneys and other vital organs.
