CARBOHYDRATES

CARBOHYDRATES

Constitutes 3 elements : Carbon, Hydrogen and Oxygen.

1 gm gives 17 kJ of energy (or 4.1 kcal of energy).

Carbohydrates form a better fuel than proteins and fats because their molecules have relatively more oxygen and therefore need less molecular oxygen for oxidation than those of proteins and fats.

Main source of energy providers.

The carbohydrates of the food eaten, after being processed in the alimentary canal and liver, are supplied to the tissues mainly as glucose, often called blood sugar.

An adult man of average weight and doing moderate work needs about 500 gms. of carbohydrates daily. Growing child, nursing mother and sports-persons need more carbohydrates.

Is of 3 types : Cellulose, Sugar and Starch.

Cellulose is present in the cell-wall of plants. It cannot be digested and simply acts as roughage.

D-fructose is the sweetest of sugars. It is found in fruit juices, honey, etc.

Excess sugar is stored as glycogen in liver (by a process called glycogenesis). The sugar which is still left is converted into fat and stored in various parts of the body as adipose tissue (by a process called lipogenesis). In case the food provides inadequate glucose,

reserve glycogen is converted into glucose for use in energy production. This

conversion is known as Glycogenolysis.

•   Sources of Carbohydrates are : 3 main cereals (wheat, rice and maize), sugarcane, milk (contains lactose-a  type of sugar), fruits, honey, beet, etc. ¹   Structurally speaking, carbohydrates are of 3 types :

•      Monosaccharides : They are the simplest carbohydrates and are made up of on*, unit only (eg : glucose, fructose, galactose). These have six carbon atoms.

•      Disaccharides : Consist of 2 units of monosaccharides (eg : sucrose, lactose and maltose)

•      Polysaccharides : Those carbohydrates which contain a no. of monosaccharide units (eg : starch in plants and glycogen in animals).

•      During the process of digestion, all carbohydrates are broken down to monosaccharides.