Threonine, an amino acid, has both an acid group and a basic group in its structure (CH3-CH(OH)-CH(NH)-COOH). In aqueous solution it exists predominantly as a self-neutralized species called a zwitterion (CH3-CH(OH)- CH(NH3*)-COO). The zwitterion therefore behaves both as an acid and as a base, according to the equilibria at 25C: CH3-CH(OH)-CH(NH3)-COO(aq) + HO(2) CH3-CH(OH)-CH(NH3)-COO (aq) + HO(2) CH3-CH(OH)-CH(NH,)-COO^(aq) + HyO*(aq) CH3-CH(OH)-CH(NH3)-COOH(aq) + OH (aq) Calculate the pH of a 0.178 M aqueous solution of threonine at 25 C. (Hint: You may need to take account of the autoionization of water.) pH = JSmol Jmol Model of Threonine in the Zwitterionic Form. K = 3.7E-11 Kb =4.3E-12