Carbohydrates

Carbohydrates are the chief energy providers of the organism. They are made up of carbon, hydrogen and oxygen.

Function

The bonds between carbon and hydrogen are broken down with the help of oxygen to give energy (oxidation). Carbohydrates produce 4.1kcal/g energy under laboratory conditions. This is called calorific value. However, in the body they produce 4kcal/g of energy. This is called physiological fuel value.

Although fats yield more energy per gram (9kcal/g) and proteins (4kcal/g) yield just as much, carbohydrates are preferred as regular sources of energy. This is because they contain more oxygen molecules and therefore require lesser number of oxygen molecules for oxidation to give energy. Almost 80% of our energy requirements are met by carbohydrates. A normal adult requires about 500g of carbohydrates per day. However, people like sportsmen, lactating mothers, mountaineers and labourers may need more. In addition to providing energy, some of the carbohydrates also change to intermediate forms that go to make amino acids.

Sources

of carbohydrates are cereals such as the rice, wheat, maize, ragi, barley and sorghum (jowar) and other foods like potatoes, sugar cane, sugar beet, sweet potato, banana, tapioca, grapes, etc.

Food commonly contains three types of carbohydrates - starch, sugar and cellulose.

Starch

is a complex carbohydrate which breaks down into simpler carbohydrates like glucose.

Sugars

are simple carbohydrates that are sweet to taste. In nature, it is found in grape juice. Common sugars are sucrose (cane sugar), glucose (grapes) and lactose (milk). All carbohydrates are ultimately broken down into glucose, which is then transported to various parts of the body through blood. It is oxidised to release energy during respiration. Thus, glucose gives instant energy when injected directly into blood during emergencies. It is also stored the in skeletal muscles that do more work. Excess glucose is stored as glycogen in the liver and as fats in body tissues.

Cellulose

is the cell wall material and cannot be digested by humans. It provides the roughage in the diet.

Functions of carbohydrates

a) The carbohydrates are the chief energy providers.

b) They are also the constituents of bodily tissues.

c) They (fibres) provide roughage in the diet.