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 Except glycine, all other naturally occurring a-amino acids are
optically active, since the a-carbon atom is asymmetric