Nutrition includes all those processes of a living being whereby it takes food, digests it, and utilizes the digested materials for (i) its survival, (ii) growth, and (iii) repair of worn-out parts the body. Digested and assimilated materials become the food for cells.
Nutrition is required for the following purposes.
Body cells multiply regularly. They increase in size also. For these processes and to replace damaged and worn-out tissues, new protoplasm is continuously required. Food helps in the formation of new protoplasm in the body.
2. Release of Energy:
Energy is required for performing various life process like ingestion, digestion, absorption, movement, co-ordination, secretion, circulation, respiration, etc. energy required for these processes is released by the oxidation of food in the protoplasm.
3. Formation of Organic substance:
Many organic substances like enzymes and hormones are required by the living beings. These are produced from the raw materials provided by food.
4. Regulating Metabolic Processes:
Food is required by the organisms for various other metabolic activities. For maintaining and repairing various parts, the food provides basic raw materials.
5. Giving resistance:
Food is also helpful in building up the resistance against diseases. Nutrition is classified into two types-autotrophic and heterotrophic.