Protein Structure & Biological Function

Protein Structure and Biological Function.

Proteins are macromolecules with a high molecular mass, which are involved in every cell process. Many of these complex organic compounds are enzymes, which are catalysts for biochemical reactions - they accelerate the reactions in which they are involved. Proteins can also be found performing structural roles, for example in the cytoskeleton; or enabling functions such as the joining together of molecules, immune response and the transmission of information within and between cells. Proteins are a vital part of an animals’ diet, as they contain certain amino acids which animals are incapable of manufacturing. Proteins are linear polymers which are constructed of 20 types of amino acids, in a linear polypeptide chain. The sequence in which the amino acids are placed in a given chain is defined by a gene. Proteins always contain Oxygen, Hydrogen, and Carbon and Nitrogen. (PAULING, L., COREY, R.B. et al, 1951).

There are four levels of protein structure, which are known as primary, secondary, tertiary and quaternary structure respectively. Not all proteins have a quaternary structure. Primary structure consists of amino acids, joined by peptide bonds which form a linear polypeptide chain. Secondary structure is defined when hydrogen bonds form between different amino acids in the polypeptide chain, forming either an alpha helix (coil), or a beta-pleated sheet. Hydrogen bonds maintain the proteins’ shape. Tertiary structure occurs when the alpha-helix or beta pleated sheet folds and twists into a stable structure, again held in place by covalent bonds. The way the helix or pleated sheet does this is dependent on which, and where amino acids are present in the polypeptide chain. When two or more proteins in tertiary structure join together to form a larger molecule, it is considered to have quaternary structure. The correct function of any given protein is only realised when the protein achieves its final three-dimensional...