An unidentified amino acid has pKa values (of the ionizable groups) of 2.2, 9.1, and 10.5. Its side chain is an amino group. Using the table above, determine the isoelectric point of the amino acid

TABLE 3.2 pk, values of acidic and basic constituents of free amino acids at 25C Amino acid pKa value Carboxyl Amino Side group group chain Glycine 2.4 9.8 Alanine 2.4 9.9 Valine 2.3 9.7 Leucine 2.3 9.7 Isoleucine 2.3 9.8 Methionine 2.1 9.3 Proline 2.0 10.6 Phenylalanine 2.2 9.3 Tryptophan 2.5 9.4 Serine 2.2 9.2 Threonine 2.1 9.1 Cysteine 1.9 10.7 8.4 Tyrosine 2.2 9.2 10.5 Asparagine 2.1 8.7 Glutamine 2.2 9.1 Aspartic acid 2.0 9.9 3.9 Glutamic acid 2.1 9.5 4.1 Lysine 2.2 9.1 10.5 Arginine 1.8 9.0 12.5 Histidine 1.8 9.3 6.0