Question

Biological function of lipids are
A. Source of energy
B. Insulating material
C. Maintenance of cellular integrity with other macromolecules
D. All of the above

Answer 1

Lipids add richness and flavour to food and as a cooking medium to fry or cook food. They improve the texture of various preparations and are found in plant, animal and marine foods.

Complete Answer:
- The property that sets lipids separately from other major nutrients is their solubility in organic solvents such as ether, chloroform, and acetone. If lipids are defined according to this property, which is normally the case, the range of their function becomes quite broad.
- It encompasses not only dietary sources of energy and the lipid constituents of cell and organelle membranes but also the fat-soluble vitamins, corticosteroid hormones, and certain intermediaries of electron transport, such as coenzyme Q.
- Among the many compounds classified as lipids, only a small number are significant as dietary energy sources or as functional or structural constituents within the cell.

The classification of the lipids include the following:
1. Simple lipids
Fatty acids
b. Triacylglycerols, diacylglycerols, and monoacylglycerols
c. Waxes (esters of fatty acids with higher alcohols)
2. Compound lipids
Phospholipids
b. Glycolipids (carbohydrate containing)
c. Lipoproteins (lipids in association with proteins)
3. Derived lipids: These are derivatives such as sterols and straight-chain alcohols obtained by hydrolysis.

- Fats are a significant class of biomolecules. They are compounds of carbon, hydrogen and oxygen where the relation of hydrogen and oxygen is less than that of water.
- Lipids are a strong source of energy and serve for long term energy storage in the body of animals and plants. Their respiratory quotient is < 1.
- About 9 calories are provided by one gram of fat as compared to 4 by carbohydrates. It also acts as insulating material because they are poor conductors of heat. Most of the animals have a coating of fat below the skin acting as insulating material.
- Fats also serve as structural biomolecules for example conjugate lipid molecules like phospholipids, glycolipids, sphingolipids etc.

Note: Fat provides 9 kcal energy / 1 gram. It is the best source of energy and it stores energy for the future in the body. Organic compounds are composed of carbon, hydrogen and oxygen.