An alpha-amino acid contains an acidic carboxyl group and a basic amino group, so in solution it does not exist mainly as the un-ionised neutral molecule. Instead, an internal proton transfer converts -COOH to -COO^- and -NH2 to -NH3^+, producing a dipolar ion called a zwitterion. The isoelectric point is the pH at which the concentration of this zwitterion is maximised and the average net charge on the molecule is exactly zero, so it experiences no net force in an applied field and does not migrate toward either electrode. A fully protonated cation would migrate toward the cathode, and a dianion would migrate toward the anode, so both predict movement and are rejected. The intact neutral -COOH/-NH2 form is not the dominant species in aqueous solution because the internal acid-base reaction is strongly favoured. This reflects the NCERT treatment of the dipolar nature of amino acids. As a plausibility check, raising the pH above the isoelectric point gives a net negative ion that moves to the anode, and lowering it gives a cation, confirming that zero migration occurs only at the isoelectric pH.