Peptide Bond Formation by Condensation

Steps:

• Identify peptide bond as covalent amide link between carboxyl (COOH) of one amino acid and amino (NH2) group of another.
• Recognize process as dehydration synthesis, where H from NH2 and OH from COOH form H2O, leaving C-N bond.
• Examine diagrams for two amino acids approaching with water molecule departing and new bond indicated.
• Select diagram matching this reaction mechanism.

Why A is correct:

• Depicts condensation reaction per biochemistry definition, showing carboxyl carbon attacked by amino nitrogen with H2O release to form peptide linkage.

Why the others are wrong:

• B: Illustrates hydrolysis, adding water to break a bond.
• C: Shows side-chain interaction like ionic bonding, not main-chain peptide formation.
• D: Depicts ester bond or unrelated linkage, lacking amide structure.

Final answer: A