Q.There is a definite sequence of amino acids linked with each other in each polypeptide chain of protein. This sequence of amino acids denotes

The order/sequence of amino acids joined by peptide bonds in a chain is the protein's primary structure. Correct option (a).

Protein structure has four levels:

• Primary: the exact sequence/order of amino acids linked by peptide (amide) bonds in each chain.
• Secondary: local folding into alpha-helix or beta-pleated sheet, held by hydrogen bonds.
• Tertiary: overall 3-D folding of the whole chain.
• Quaternary: assembly of two or more polypeptide sub-units. …