If the pH of the solution is above the pH of the isoelectric point of the amino acid, the amino acid will contain the COO- ion and will be attracted towards the positive terminal. If the pH of the solution is below the pH of the isoelectric point of the amino acid, the NH3+ form will exist and it will move to the negative treminal. If the pH is the same as the isoelectric point, then both the COO- and the NH3+ groups will exist and the zwitter ion will not be attracted to either the positive or negative terminal, it will remain in its position.
Great link for electrophoresis
