What are proteins ? Discuss different structures of proteins.

Explanation

Proteins are complex compounds formed by many `alpha`- amino acid units. They are linked through peptide bonds, having molecular mass greater than 10,000u.
Structure of proteins
1) Primary structure : It refers to sequences in which various amino .acids are linked to one another in protein.
ii) Secondary structure : The conformation in which polypeptide chains are formed as a result of H-bondiilg. There are two different secondary structures of protein.
a) `alpha`- Helix structure : ` alpha` - Helix structure may be right handed or left handed. In this, H - bond is formed between the C = O of one amino acid and N -H of fourth amino acid residue in the chain pleated.
b) `beta `- -flat sheet : In t!iis, polypeptide chains lie side by side in a zig-zag manner. They have alkyl groups on same side situated at fixed distance. The two polypeptide chains are held together by intennolecular H-bonds.
iii) Tertiary structure : It refers to the complete three dimensional structure of proteins.
iv) Quaternary structure : It refers to spatial arrangement of subunits in a polypeptide chain.