α-Amino acids behave as dipolar ion or as Zwitterion due to the transfer of a proton (H+) from carboxylic group to the amino group in the same molecule.
In acidic medium, the cation formed migrates towards cathode while in the basic medium anion migrates towards anode on passing an electric current. At a certain pH of the medium called an isoelectric point of an α-amino acid, the Zwitterion behaves as neutral and does not migrate to any electrode on passing current. The iso-electric points are in the pH range of 5.5 to 6.3.
