Question

What are the main functions of proteins in living things?

Answer 1

Hint: All nutrients present in the body have an important role in living organisms. Proteins are made up of amino acids which help in the production of hormones, blood components, vitamins etc. Depending on its types protein performs different functions.

Complete answer:
The main functions of protein include the development of cells and tissues by the formation of the colloidal complex of protoplasts, cell membrane, organelles, matrices and fibres. It forms fibrous protein keratin in hair, feathers, horny layer of skin, nails etc. By forming enzymes it catalyzes biochemical reactions which help in metabolism. It also produces proteinaceous hormones like insulin, parathyroid etc. The contractile protein like myosin and actin produces movement and locomotion with the help of fibres. The immunoglobulins proteins help in the defence mechanism of the body. The storage protein like casein in milk, albumin in egg white and glutelin in cereals helps in the nourishment of the body. Iron storing protein in animals is ferritin. Protein like rhodopsin and iodopsin are present in the rods and cones of the eye which helps in the perception of the image. Protein like fibrinogen and thrombin helps in blood clotting and it also helps to check the bleeding from injuries. The mucoproteins are present in mucus produced by the salivary gland and by the mucus gland of the alimentary canal which protects the lining of the alimentary canal.

Note:
The protein was coined by Gerardus Johannes Mulder from the Greek word proteins which means 'the first rank' because the protein is the most important macromolecules of organisms and it constitutes $12\%$ of the cell content after water.