question_answer 39)

  Schematically represent primary, secondary and tertiary structures of a hypothetical polymer say for example a protein.

Answer:

                  Proteins are the large-sized, heteropolymeric macromolecules having one or more polypeptides (chains of amino acid). Primary Structure The primary structure of a protein is the linear sequence of amino acidstructural units and partially comprises its overall biomolecular structures. The amino acidsare linked together in a sequence by peptide bonds. In the primary structure of protein initiate from an amino-terminal (N) to the carboxyl terminal (C) end, Amino acids in a chain    First amino acid Last amino acid represents right and  of polypeplide chain Secondary Structure It is a three dimensional form of local segments of bipolymers such as proteins. Secondary structure of proteins is defined by hydrogen bonds betweenbackbone amino and carboxyl groups. Mainly secondary structure in proteins possess two forms, i.e., helix and p-pleated sheet. helix is a polypeptide chain spirally coiled to form a right handed helix. This helix may becoiled regularly at places and at some places randomly coiled. The helix is stabilised by many hydrogen bonds which are formed between ? CO of one amino acid and ? NHgroup of next fourth amino acid. pleated sheets two or more polypeptide chains are joined together by intermolecularhydrogen bonds to produce a sheet like structure instead of fibre as in a-helix. Thepolypeptide strands in a sheet may run parallel in same direction, e.g., keratin or in oppositedirection called antiparallel (sheet, e.g., fibroin. Tertiary structure involves interactions that are caused by the bending and folding ofa-helix or p-sheets leading to the formation of rods, spheres of fibres. Such interactions aretypically conferred by H-bonds, ionic bonds, covalent bonds, van der Waat's interactions and hydrophobic interactions or disulphide linkages. It gives the protein a three dimensionalconformation.