How many peptide linkages are present in a nonapeptide?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 8
A peptide linkage (–CO–NH–) forms between the –COOH group of one amino acid and the –NH2 group of the next, with loss of a water molecule. In a chain each new amino acid adds one linkage:
Dipeptide: 2 amino acids, 1 peptide linkage.
Tripeptide: 3 amino acids, 2 peptide linkages.
In general: n amino acids, (n − 1) peptide linkages.
A nonapeptide has 9 amino acids, so it has 9 − 1 = 8 peptide linkages.
NCERT (2026-27 edition):
10.2.3 Structure of Proteins – “If a third amino acid combines to a dipeptide, the product is called a tripeptide. A tripeptide contains three amino acids linked by two peptide linkages. Similarly when four, five or six amino acids are linked, the respective products are known as tetrapeptide, pentapeptide or hexapeptide, respectively.”