Peptide Bonds (CIE A Level Chemistry)

• Each amino acid contains an amine (-NH₂) and carboxylic acid (-COOH) group
• The -NH₂ group of one amino acid can react with the -COOH group of another amino acid in a condensation reaction to form a dipeptide
  • The new amide bond between two amino acids is also called a peptide link or peptide bond

• Since this is a condensation reaction, a small molecule (in this case H₂O) is eliminated
• The dipeptide still contains an -NH₂ and -COOH group at each end of the molecule which can again participate in a condensation reaction to form a tripeptide

A peptide bond is an amide bond between two amino acids

• A polypeptide is formed when many amino acids join together to form a long chain of molecules

A polypeptide is a long chain of amino acid molecules joined together