Natural amino acid is represented as
When the characteristic feature of the side chain R, is ‘H’ for glycine and (H3C)2CH- for Valine, how many peptide bonds will be present in Glycylvaline , a dipeptide?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → 1
Each peptide bond joins two amino acid units:
Dipeptide (2 amino acids): 1 peptide bond
Tripeptide (3 amino acids): 2 peptide bonds
In general, n amino acids are joined by n − 1 peptide bonds.
In glycylvaline (Gly-Val), the –COOH of glycine (R = H) joins the –\( \ce{NH2} \) of valine (R = \( \ce{(CH3)2CH} \)–):
\( \displaystyle \ce{H2N-CH2-COOH + H2N-CH(R)-COOH -> H2N-CH2-CO-NH-CH(R)-COOH + H2O} \)
So a dipeptide, glycylvaline, contains 1 peptide bond.
NCERT (2026-27 edition):
Structure of Proteins
