This behaviour is due to the presence
of both acidic (carboxyl group) and basic (amino
group) groups in the same molecule In aqueous
solution, the carboxyl group can lose a proton
and amino group can accept a proton, giving rise
to a dipolar ion known as zwitter ion This is
neutral but contains both positive and negative
charges In zwitter ionic form, amino acids show amphoteric behaviour as
they react both with acids and bases