Lipids

Lipids
Lipids constitute a heterogeneous group of compounds of biochemical importance. Lipids may be defined as compounds which are relatively insoluble in water, but freely soluble in non-polar organic solvents, such as benzene, chloroform, ether, hot alcohol, acetone, etc.
CLASSIFICATION OF LIPIDS
Detailed classification Based on the chemical nature, lipids are classified as:
1. Simple lipids: They are esters of fatty acids with glycerol or other higher alcohols.
2. Compound lipids: They are fatty acids esterified with alcohol; but in addition they contain other groups. Depending on these extra groups, they are sub classified in
a. Phospholipids, containing phosphoric acid.
b. Non-phosphorylated lipids
3. Derived lipids: They are compounds, which are derived from lipids or precursors of lipids, e.g. fatty acids, steroids. For details of cholesterol and steroids
4. Lipids complexed to other compounds
Functions of Lipids
1.Storage form of energy (triacylglycerol)
2. Structural components of biomembranes (phospholipids and cholesterol)
3. Metabolic regulators (steroid hormones and prostaglan-dins
4.Act as surfactants, detergents and emulsifying agents amphipathic lipids)
5.Act as electric insulators in neurons
6. Provide insulation against changes in external temperature subcutaneous fat
7. Give shape and contour to the body
8. Protect internal organs by providing a cushioning effect pads of fat)
9. Help in absorption of fat soluble vitamins (A, D, E and K(
10. Improve taste and palatability of food.
FATTY ACIDS
Fatty acids, are included in the group of derived lipids. It is the most common component of lipids in the body. They are generally found in ester linkage in different classes of lipids. In the human body, free fatty acids are formed only during metabolism. Fatty acids are aliphatic carboxylic acids and have the general formula, R—CO—OH, where COOH (carboxylic group) represents the functional group. Depending on the R group (the hydrocarbon chain), the physical properties of fatty acids may vary.