The term ‘Lipids’ is applied to a group of naturally occurring substances characterized by their insolubility in water, greasy feel and solubility in organic solvents. They occur in the plant and animal kingdom. Fats are a more concentrated form of storage of energy than carbohydrates. In the presence of adequate supply of carbohydrates, fat is stored in the adipose(fatty) tissue.
Chemical composition of lipids
Fat is a complex molecule constituting a mixture of fatty acids and an alcohol, generally glycerol. Like carbohydrates, it contains carbon, hydrogen and oxygen, but it differs from a carbohydrate in that it contains more carbon and hydrogen and less oxygen. When oxidized, it gives 9 kilocalories. A molecule of fat consists of 3 molecules of fatty acids and one molecule of glycerol. It is also known as triglyceride.