What is the isoelectric point of lysine within in +/- 1 pH unit?

Question

Quizplus · Accepted Answer

The isoelectric point (pI) of lysine is approximately 9. This is the pH at which the amino acid has no net charge, as the positively charged amine group (NH3+) is balanced by the negatively charged carboxyl group (COO-). Since the question asks for the +/- 1 pH unit, the answer is C, as lysine's pI would fall within the range of 8 to 10 pH units. Answer choices A (pH 3) and B (pH 6) are well outside of this range, and choice D (pH 12) is also too far from the actual pI.

What Is the Isoelectric Point of Lysine Within in +/-