What is the ionizable nature of amino acids?

The chemical and physical properties of amino acids are essentially

of the amino, carboxyl and the R functional groups. Based on number of amino and carboxyl groups, there are acidic (e.g., glutamic acid), basic (lysine) and neutral (valine) amino acids. Similarly, there are aromatic amino acids (tyrosine, phenylalanine, tryptophan). A particular property of amino acids is the ionizable nature of –NH₂ and –COOH groups. Hence

in solutions of different pH, the structure of amino acids changes.