How many amino acids are present in insulin?

The correct answer is Option (2) → 51

NCERT (2026-27 edition):
10.2.3 Structure of Proteins – “… A polypeptide with more than hundred amino acid residues, having molecular mass higher than 10,000u is called a protein. However, the distinction between a polypeptide and a protein is not very sharp. Polypeptides with fewer amino acids are likely to be called proteins if they ordinarily have a well defined conformation of a protein such as insulin which contains 51 amino acids.”