Biomolecules: JEE Main Chemistry Question with Solution
A short peptide on complete hydrolysis produces 3 moles of glycine (G), two moles of leucine (L) and two moles of valine (V) per mole of peptide. The number of peptide linkages in it are
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Hint 1 of 2
How many total amino acid residues make up one molecule of the peptide?
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Step-by-step solutionView
Correct answer
The peptide contains 7 amino acid residues in total, which corresponds to 6 peptide linkages.
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Solution
StepWorking
01given
Per mole of peptide, complete hydrolysis produces:
- 3 moles of glycine (G)
- 2 moles of leucine (L)
- 2 moles of valine (V)
02find
Find the total number of peptide linkages present in one molecule of the peptide.
03strategise
A linear peptide formed from n amino acid residues contains (n−1) peptide bonds because each peptide bond forms between two adjacent amino acid units with the loss of one water molecule.
04execute
Total number of amino acid residues n=3+2+2=7.
Therefore, the number of peptide linkages is n−1=7−1=6.
✓verify
Hydrolysis of 6 peptide bonds requires 6 molecules of H2O and yields 6+1=7 amino acid molecules per peptide molecule, which matches the given 3+2+2=7 amino acids.
Hints that build this answer step by step
How many total amino acid residues make up one molecule of the peptide?
7 residues (3 Gly + 2 Leu + 2 Val)
For an open-chain peptide composed of n amino acid residues, how many peptide linkages (bonds) are present?
Could the peptide be cyclic, meaning it would have 7 peptide bonds?
In standard JEE problems, unless a 'cyclic peptide' is explicitly stated, short peptides are assumed to be open/linear chains with free N-terminal and C-terminal ends.