What are proteins? Describe different biological functions of proteins.
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★ Proteins:
- Proteins are the long chain polymers of amino acids and possess high molecular weight. They contain C, H, O and N. The presence of N distinguishes them from carbohydrates and lipids. Some proteins contain sulphur, while few proteins contain phosphorus also. Cells contain a large number of proteins.
★ Biological functions of proteins:
The biological importance of proteins is as follows:
- i. Membrane proteins: Cell membrane consists of proteins and lipids. All membrane bound cell organelles have lipids and proteins in their membranes.
- ii. Enzymes: All enzymes are proteins. Enzymes may contain some other non-protein part also along with protein. e.g. Amylase.
- iii. Hormones: Hormones are proteins. They play an important role in the regulation of metabolic reactions in the body, e.g. Insulin, thyroxine.
- iv. Transport protein: Haemoglobin which is present in R.B.C. of man is a type of protein. It is useful for transportation of oxygen.
- v. Contractile protein: Muscle fibres consist of proteins, which help in contraction. e.g. Myosin.
- iv. Structural protein: These proteins form parts of cells or tissues. e.g. Keratin is present in hair and skin, while elastin is present in connective tissue.
- vii. Defensive proteins: Useful for the protection of body. e.g. Immunoglobin, thrombin for clotting of blood.
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