The peptide formation involves two amino acids covalently joined together between the carboxyl group of one amino acid and the amino group of another.

This reaction is a condensation reaction involving removal of elements of water from the two molecules. The resulting product is called a dipeptide. The newly formed covalent bond connecting the two amino acids is called a peptide bond. Once an amino acid is incorporated into a peptide, it becomes an amino acid residue. Multiple amino acids can be joined together to form a longer chain of amino acid polymer.