In proteins, how are peptide bonds formed between two amino acids?

• A. By hydrolysis of an existing amide bond, consuming $H_{2}O$ to link the amino acids
• B. By a condensation (dehydration) reaction between the carboxyl group of one amino acid and the amino group of another, releasing $H_{2}O$
• C. By an oxidation reaction that creates a disulfide bond between two cysteine side chains
• D. By formation of an ionic (salt) bridge between the amino and carboxyl groups without loss of any small molecule

Answer: (B)