Question

Few unique features of A, B and C are

• A. A= Amino acids are joined by peptide bonds forming polypeptide strands. B= Polypeptide strands may form $\beta$-pleated sheets due to additional hydrogen bonding.C= Polypeptides are modified to specific shapes due to stabilization by additional disulphide and ionic bonds (other than peptide and hydrogen bonds).
• B. A= Polypeptide strands may form $\beta$-pleated sheets due to additional hydrogen bonding. B= Amino acids are joined by peptide bonds forming polypeptide strands. C= Polypeptides are modified to specific shapes due to stabilization by additional disulphide and ionic bonds (other than peptide and hydrogen bonds).
• C. A= Polypeptides are modified to specific shapes due to stabilization by additional disulphide and ionic bonds (other than peptide and hydrogen bonds). B= Amino acids are joined by peptide bonds forming polypeptide strands. C= Polypeptide strands may form $\beta$-pleated sheets due to additional hydrogen bonding.
• D. A= Proteins are joined by peptide bonds forming polypeptide strands. B= Polypeptide strands may form $\beta$-pleated sheets due to additional hydrogen bonding. C= Polypeptides are modified to specific shapes due to stabilization by additional disulphide and ionic bonds (other than peptide and hydrogen bonds).

Answer 1

The correct option is A A= Amino acids are joined by peptide bonds forming polypeptide strands.

B= Polypeptide strands may form $\beta$-pleated sheets due to additional hydrogen bonding.

C= Polypeptides are modified to specific shapes due to stabilization by additional disulphide and ionic bonds (other than peptide and hydrogen bonds).

The structure of any given protein can be classified into four types. These are primary, secondary, tertiary and quaternary. The primary structure of a protein is just simply the sequence of amino acids present in the protein i.e., their name and the order in which they are present. Secondary structure of a protein is formed by formation of hydrogen bonds in the primary structure. Two common types of secondary structure of proteins found in nature are alpha helix and beta sheets. Now, the folding of this secondary structure upon itself by ionic or disulphide bridges leads to the formation of tertiary structure, the third level in the structure of proteins. Finally, the association of two subunits i.e., two tertiary structures and further folding thereby in a characteristic way results in the formation of quaternary structure which is usually the functional form of the protein.

Therefore, the correct answer is option A.