Which of the following amino acids has an isoelectric pH of 3.2?

Question

Quizplus · Accepted Answer

The isoelectric point (pI) of an amino acid is the pH at which the net charge on the molecule is zero. Glutamic acid has a side chain carboxyl group (COOH) which ionizes at a pH below its pKa (4.2), resulting in a negatively charged carboxylate group (COO-). At pH 3.2, this group will have a full negative charge, while the amino group (NH3+) on the other end of the molecule will have a partial positive charge. Therefore, the net charge of the molecule will be zero at pH 3.2, making this the isoelectric pH of glutamic acid.

Which of the Following Amino Acids Has an Isoelectric PH