Proteins play a crucial role in vir­tually all biological processes

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The complex organic nitrogenous substances found in living cells (G.J. Milder, 1840) are known as proteins. The term protein (Gr.proteios- holding the first rank) suggested by Berzelius (1938), in itself speaks about pivotal position they occupy in living world. They are primarily concerned in (1) structural architecture and (2) func­tioning of the living system.

Proteins play a crucial role in vir­tually all biological processes,viz,

(i) Transport and storage (haemoglobin in blood, myoglobin in muscles, both as oxygen carriers-egg's white, ovalbumin, glutelin in cereals, iron storing ferritin in animals);

(ii) Coordinated motion (muscle movement, elastic and non-elas­tic fibres in connective tissues and contractile fibres- actin and myosin in muscles),

(iii) Mechanical support (tensile strength of skin and bone collagen, a fibroses protein),

(iv) Immune protection (antibodies),

(v) Generation and transmission of nerve impulse (receptor proteins),

(vi) Control of growth and differentia­tion (sequential expression of ge­netic information),

(vii) Enzymatic catalysis (unique role in determining the pattern of chemical transformation in bio­logical systems),

(viii) Stable colloidal behaviour (the pro­tein ions in solution repel one an­other and attract the water mol­ecules to orient around).

Proteins are the most abundant and most varied of the macromolecules of the living cells. They constitute about 50% of the dry weight of cells. These macro­molecules are really large, ranging in molecular weight from several thousand to several million. They are the polymers of amino acid monomers. The proteins are made up of 20 different types of natu­rally occurring amino acids.


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