Biological significance of lipids
- Chief food storage compounds: Body lipids reservoir of potential chemical energy. Triacylglycerol lipids are the basic food reserves of organisms. They become readily available in times of restricted nutrition for the operation of numerous endergonic processes necessary for the maintenance of life. In vertebrates, lipid is distributed in all organs as well in certain depots like subcutaneous adipose tissue, around the heart and kidneys and particularly along the peritoneal membranes, mesentries that envelope the intestine The liver too is an important fat depot. Its total fat store is in balance with the reserves in other depots.
- Structural component of cells: Lipids are structural components of cellular membranes, where they contribute to controlling the movement of materials into and out of the cells. The structural fats are mostly phospholipids and form structural complex with proteins.
- Rich source of respiratory energy: As the principle form in which energy is stored in the body, triacylglycerol has definite advantages over carbohydrate or protein. Its caloric value is over twice as great and it is associated with less water in storage. Triacylglycerol is, therefore, the most concentrated form in which potential energy can be stored.
- Carriers of essential compounds: A minimal amount of lipid is essential in the diet to provide an adequate supply of certain polyunsaturated fatty acids and of fat soluble vitamins like A,D&E. Dietary lipid is also essential for the efficient absorption of these substances from the gastrointestinal tract.
- Enzyme activation: Many enzymes require lipid molecules for maximal activation. Examples are microsomal enzyme glucose 6-phosphatase.
- Hormone synthesis: Adrenal corticoids, sex hormones and vitamin D and are synthesized from lipid derivatives.
- Heat insulation: Much of the lipids of mammals is located subcutaneously and acts as an insulator against excessive heat loss to the environment. Subcutanous fat deposits are higher in aquatic animals.
- Mechanical Protection: The subcutaneous lipid depots also insulate the body against mechanical trauma.