Maintain life organisms performs some basic function is called nutrition. Nutrition is one of the basic function of life in which intake of food, digestion, absorption, assimilation and egestion of undigested foods are included.


Nutrient are the substance by which an organism get energy or it is used for biosynthesis of its body.

1. Carbohydrate

Carbohydrates are organic compounds in which the ratio of Carbon, Hydrogen and Oxygen is 1 : 2 : 1. Carbohydrate in the form of sugar and starch are major intake m animals and human. 50 to 75% energy is obtained by oxidation of carbohydrate. Carbohydrate containing aldehyde group is called aldose and with ketone group is called ketose. Carbohydrates are dericatives of polyhydroxy alcohols.

Classification of carbohydrate :
Carbohydrates are classified into three major gropus :
(a) Monosaccharides : These are the simple sugar made up of single polyhydroxy or ketone unit. Most abundant monosaccharides found in nature is glucose containing six carbon atom. Triose, Tetrose, Pentoses, heptoses are the type of monosaccharides.
» Glucose is a type of hexose sugar.

(b) Polysaccharides : When 2 to 10 monosaccharides join together they form oligosaccharides. They are usually crystalline in nature and sweet in test. Maltose sucrose, lactose are disaccharides made up of two monosaccharides.

(c) Polysaccharides : These are the compound of sugar which are formed due to joining large number of monosaccharide. There are insoluble and tasteless. Some example of polysaccharides are starch, glycogen, cellulose, etc.

Function of Carbohydrate
1. Carbohydrate works as fuel. During the process of respiration, glucose break into into CO2 and H2O with the release of energy. One gram of glucose gives 4.2 kilo calories energy.
2. Glucose is the source of immediate energy production in the cell.
3. Nucleic acids are polymers of nucleosides and nucleotides and contain pentose sugar.
4. Lactose of milk is formed from glucose and glactose.
5. Glucose is used for the formation of fat and ammo acid.
6. Carbon skeleton of monosaccharide, is used in the formats of fatty acid, chitin, cellulose etc.

2. Protein

Protein word was first use by J. Berzelius. This is a complex organic compound made up of 20 type of ammo acid . Approximately 15% of the human body is made up of protein. Nitrogen is present in protein in addition to C, H & O.
» N2 gas is essential for protein synthesis.
Twenty type of amino acid are necessary for human body, out of which 12 are synthesized by body itself and remaining 8 are obtained by food are called essential amino acid.

Types of proteins :
On the basis of chemical composition. It is divided into three types :
» Simple Protein : It consists of only amino acid. Examvle-Albumins, Globulins, Histones etc.

Conjugated Protein : Having some another chemical compounds in addition to amino add. Examvle-Chromoprotein, Glycoprotein etc.

» Derived Protein Tt is derived from the partial digestion of natural proteins or its hydrolysis. Example-Peptone, Peptide, Proteinase etc.

Function of Protein :
» It takes part in the formation of cells, protoplasm and tissues.
» These are important for physical growth. Physical growth hampers by its deficiency. Lack of proteins causes Kwashiorkor and Marasmus diseases in children.
» In case of necessity these provide energy to the body.
» Control the development of genetic characters.
» Helpful in conduction also.

3. Fats

Fat is an ester of glycerol and fatty add.
In these carbon, hydrogen and oxygen are present in different quantities, but proportionally less oxygen than carbohydrate.
Normally fat remains as solid at 20°C temperature, but if it is in liquid form at this temperature, this is called oil.
Fatty adds are of two types - Saturated and unsaturated. Unsaturated fatty adds are found in fish oil and vegetable oil. Only coconut oil and palm oil are the examples of saturated oil.
9.3 kilo calorie energy is liberated from 1 gram fat.
Normally an adult person should get 20-30% of energy from fat.

Main functions of fat :
1. It provides energy to the body.
2. It remains under the skin and prevents the loss of heat from the body.
3. It make the food material testy.
4. It protects different parts of the body from Injury.

Due to the lack of fat skin gets dried, weight of the body decreases and the development of the body checked.
Due to the excessiveness of fat the body gets fatty, heart disease takes place and blood pressure increases.

4. Vitamins

Vitamin was invented by Sir F. G. Hopkins. The term vitamin was coined by Funk.
Vitamins are organic compound required in minute quantities. No calorie is obtained from it, but it is very important in regulating chemical reactions in the metabolism of the body.

On the basis of solubility, vitamins are of two types :
(a) Vitamin soluble in water: Vitamin-B and Vitamin-C.
(b) Vitamin soluble in fat: Vitamin-A, Vitamin-D, Vitamin-E and Vitamin-K.

5. Minerals

Mineral is a homogenous inorganic material needed for body. These control the metabolism of body.
» Deficiency of calcium and iron is generally found in pregnant women.

6. Water

Human gets it by drinking. Water is the important component of our body. 65-75% weight of the body is water.

Main functions of water :
1. Water controls the temperature of our body by sweating and vaporizing.
2. It is the important way of excretion of the excretory substances from the body.
3. Maximum chemical reactions in the body perform through hydrolysis.