Question

Read the given statements and select the correct option.
Statement 1 : Haemoglobin is an example of quaternary structure of proteins.
Statement 2 : Haemoglobin molecule is composed of four polypeptide chains-two $\alpha$-chains and two $\beta$-chains.

• A. Both statements 1 and 2 are correct
• B. Statement 1 is correct but statement 2 is incorrect
• C. Statement 1 is incorrect but statement 2 is correct
• D. Both statements 1 and 2 are incorrect

Answer 1

Answer: (A)

Proteins are said to have quaternary structure if they consist of $2$ or more polypeptide chains united by forces other than covalent bonds (i.e., not peptide or disulphide bonds). The forces that stabilise these aggregates are hydrogen bonds and electrostatic bonds formed between amino acids on the polypeptide chains. Haemoglobin, the oxygen-transporting protein of blood, is an example of quaternary structure. This protein consists of four peptide chains of two types-$\alpha$ and $\beta$ chains that occur in pairs.