According to the given question,
Amino acids have two groups- carboxyl group and amino group.
When amino acids are in aqueous solution, the carboxyl group of the amino acid might lose a proton and the amino group present in amino acid might get a proton and form dipolar ion this is known as zwitterion.
In this zwitterion form, amino acids can behave as both acid as well as base.
And Amphoteric compounds are those who possess the behavior of both acid and base.
Hence, we can say that Amino acids show amphoteric behavior.
Final Answer:
Amino acids show amphoteric behavior because of the property of zwitterion.