Question

Give reasons for the following:

Amino acids show amphoteric behaviour.

Answer 1

Amino acids possess both an acidic carboxyl group (–COOH) and a basic amino group (–NH₂). In an acidic medium, the amino group accepts a proton to form \[\ce{-NH^+_3}\], causing the amino acid to act as a base. In a basic medium, the carboxyl group donates a proton to form –COO⁻, making the amino acid behave as an acid. Because of this dual behaviour, amino acids can react with both acids and bases and therefore show amphoteric nature.