At what pH would you expect valine, an amino acid with a neutral R group, to be in the zwitterionic form?

Question

Quizplus · Accepted Answer

The zwitterionic form of an amino acid occurs when the amino group (NH3+) and the carboxyl group (COO-) are both ionized, but the R group is neutral. At low pH, the amino group would not be protonated, and therefore would be NH2, which would not allow for a zwitterionic form. At high pH, the carboxyl group would not be ionized, and therefore would be COOH, which also would not allow for a zwitterionic form. At a pH of around 6, both the amino and carboxyl groups would be ionized, but the R group would remain neutral, allowing for the formation of the zwitterionic form.

At What PH Would You Expect Valine, an Amino Acid