If the pH of a solution is higher than a protein's isoelectric point, the protein will carry what net charge?

• A. Positive
• B. Negative
• C. Zero
• D. Depends on the protein

Answer: (B)

The isoelectric point is the pH where a protein has no net charge. As pH increases above that point, acidic groups lose protons and become negatively charged, while positive charges from basic groups are reduced. This shift makes the overall net charge negative. So, when the solution pH is higher than the protein’s isoelectric point, the protein carries a negative net charge.