The isoelectric point of an amino acid is the pH at which the molecule has no net charge. For glycine, that would be the pH at which virtually all glycine molecules are in the form +H3NCH2CO2-. If we assume that the principal equilibrium is
then at equilibrium
[H2NCH2CO2-] = [+H3NCH2CO2H]
Use this result and your answer to parr c of Exercise 146 to calculate the pH at which Equation (ii) is true. This will be the isoelectric point of glycine.