pH = 1 ⇔⇔ mediu puternic acid
aminoacizii au caracter amfoter : H2N-CH(R)-COOH ⇄⁺[H3N-CH(R)-COO⁻
in mediu acid : H3N⁺-CH(R)-COO⁻ + H⁺ ⇒H3N⁺-CH(R)-COOH (cation)
in mediu bazic : H3N⁺-CH(R)-COO⁻ +HO⁻ ⇒H2N-CH(R)-COO⁻ (anion) + H2O
⇒ H2N-CH(CH2OH)-COOH + H⁺ ⇒H3N⁺-CH(CH2OH)-COOH cation
