What do you mean by Amphoteric nature of `alpha`-amino acid ?

Explanation

Amino acids show amphoteric nature i.c: these behave both as an acid and as a base. These can be explained as follows:
Amino acids contains an acidic and basic group in the molecules in aqueous solution, these neutralize each other. The carboxyl group loses a proton while the amino group accepts it. As a result, a dipolar or Zwiller ion is form:
`underset(alpha"-amino acid")(H_(2)N-underset(R )underset(|)(CH)-COOH)hArr underset("Zwitter ion")(H_(3)N^(+)-underset(R )underset(|)(CH)-COO^(-))`
In Zwitter ionic form, `alpha` amino acids show amphoteric behaviour.
In the acidic medium `- COO^(-)` of the zwitter ion accepts a proton to form the cation (I) while in the basic medium, `NH_(3)` ion lases a proton to form the anion (II).
Thus in dipolar form `- NH_(3)^(+)` group acts as the acid while `-COO^(-)` group acts as the base.
`H_(3)N^(+)-underset((I))underset(R )underset(|)(CH)-COOH hArr H_(3)N^(+)-underset("Zwitter ion")underset(R )underset(|)(CH)-COO^(-)hArr H_(2)N-underset((II))underset(R )underset(|)(CH)-COO^(-)`