The pK_aʹs of arginineʹs α-Carboxyl group, α-Amino group and side chain are 1.8, 9.0 and 12.5, respectively. Calculate the isoelectric point. A) 7.8 B) 7.2 C) 10.8 D) 5.4

Question

Quizplus · Accepted Answer

The isoelectric point (pI) is calculated by averaging the pKa values that surround the zwitterionic form. For arginine, the relevant pKa values are 9.0 (α-Amino group) and 12.5 (side chain), so pI = (9.0 + 12.5) / 2 = 10.75, which is closest to 10.8.

The PKaʹs of Arginineʹs α-Carboxyl Group, α-Amino Group and Side

The PK_aʹs of Arginineʹs α-Carboxyl Group, α-Amino Group and Side