How do amino acids combine into a polypeptide chain? Build a dipeptide and a tripeptide

As you know, a peptide bond (O = C-N-H) arises between amino acids. From one amino acid, OH from the carboxyl group (COOH) is separated, and from the other amino acid, H from the amino group is separated. A free bond at C of the first amino acid combines with a free bond at N of the second amino acid, a peptide bond is formed:
CH3-CH (NH2) -COOH + NH2-CH2-COOH =
CH3-CH (NH2) -CO [OH + H] -NH-CH2-COOH = H2O + CH3-CH (NH2) -CONH-CH2-COOH
(Alanyl glycine dipeptide)
In the same way, the tripeptide is obtained
CH3-CH (NH2) -CONH-CH2-COOH + HO-CH2-CH (NH2) -COOH = H2O + CH3-CH (NH2) -CONH-CH2-CONH-CH (COOH) -CH2-OH (alanylglycylserine tripeptide)