34.4.2—Peptide bond formation

Condensation between the carboxylic acid group of one amino acid and the amino group of another forms an amide (peptide) bond, –CO–NH–, and removes water.

The order of amino acids matters: the free amino end is the N-terminus and the free carboxyl end is the C-terminus. A dipeptide has two residues; a tripeptide has three.

Glycine + alanine can form Gly–Ala or Ala–Gly, which are different sequences even though they contain the same two amino acids.

Peptide formation is not ionic attraction between zwitterions; it is covalent condensation at the functional groups.