Which of the following molecules is eliminated during peptide bond formation?

CONCEPT:

Peptide Bond Formation

• A peptide bond is a covalent bond formed between two amino acids during protein synthesis.
• The bond is formed between the carboxyl group (–COOH) of one amino acid and the amino group (–NH2) of another amino acid.
• During the formation of a peptide bond, a molecule of water (H₂O) is eliminated in a condensation reaction.

EXPLANATION:

• In the peptide bond formation process:

  R₁-COOH + H₂N-R₂ → R₁-CO-NH-R₂ + H₂O

  • The –OH group from the carboxyl group of one amino acid and a hydrogen atom from the amino group of another amino acid combine to form a water molecule (H₂O).
  • This results in the formation of a peptide bond (–CO-NH–) between the two amino acids.

Therefore, the correct answer is option 1: H₂O.

Explanation of Other Options:

• Option 2 (NH₃): Ammonia (NH₃) is not eliminated during peptide bond formation. It is not involved in the condensation reaction between amino acids.
• Option 3 (CH₃OH): Methanol (CH₃OH) is not a byproduct of peptide bond formation. It is not produced during the reaction between amino acids.
• Option 4 (CO₂): Carbon dioxide (CO₂) is not eliminated during peptide bond formation. It is not a byproduct of the condensation reaction between amino acids.