The isoelectric point of arginine is approximately
A) 1
B) 3
C) 5
D) 7
E) 11

Question

Quizplus · Accepted Answer

The isoelectric point of an amino acid is the pH at which it has no net charge. Arginine has three positively charged groups (amino, imino, and guanidino) and one negatively charged carboxyl group. At low pH, the amino and imino groups are protonated, giving the molecule an overall positive charge. As pH is increased, these groups gradually lose protons until the molecule reaches its isoelectric point, at which the guanidino group is no longer charged and the molecule has no net charge. For arginine, this occurs at a pH of approximately 11.

The Isoelectric Point of Arginine Is Approximately