Q.What is the physical change observed when

A protein's structure is described at four successive levels:

• Primary structure — the linear sequence of amino acids along the polypeptide chain, held together by peptide bonds.
• Secondary structure — a regular, repeating local folding pattern produced by hydrogen bonds between different parts of the chain (or between neighbouring chains): a right-handed coil (α-helix, e.g. in the keratin of hair) or a left-handed coil (β-helix), or, where separate chains are hydrogen-bonded side by side, a pleated sheet (e.g. in silk fibroin). …