Final answer:
At pH 7, glutamic acid exists predominantly in its ionized form with a net charge of -1, with the carboxyl group with a pKa of 4.3 ionized and the amino group with a pKa of 9.7 protonated.
Step-by-step explanation:
The ionization state of glutamic acid at a pH of 7 is predominantly as the anion with one negative charge (relative to the zwitterionic form), which is usually represented as Glutamic Acid (-1).
Glutamic acid has three pKa values: 2.2, 4.3, and 9.7. At pH 7, the carboxyl group with a pKa of 2.2 will be fully ionized, while the carboxyl group with a pKa of 4.3 will also be mostly ionized due to the pH being significantly higher than its pKa. The amino group with a pKa of 9.7 remains protonated, as the pH is lower than this pKa value. Using the Henderson-Hasselbalch equation, we can infer that the predominant ionic species at pH 7 is the one that has a pKa value just below the pH, which for glutamic acid would be the carboxyl group with a pKa of 4.3.
Therefore, this group will carry a negative charge, while the amino group will be in its protonated form, giving the overall molecule a net charge of -1.