At isoelectric point, a protein has

• A. No net charge
• B. Negative charge
• C. Positive charge
• D. Both B and C

The isoelectric point (pI) of a protein is a crucial concept in biochemistry. It refers to the pH at which the protein carries no net electrical charge.

Understanding the Options

• A. No net charge - This is correct. At the isoelectric point, the positive and negative charges balance each other out.
• B. Negative charge - This is incorrect at the isoelectric point.
• C. Positive charge - This is also incorrect at the isoelectric point.
• D. Both B and C - This option is not valid since neither B nor C is true at the isoelectric point.

Final Answer

The correct answer is A. No net charge. At the isoelectric point, proteins are neutral overall.