If the pH is greater than the pI in electrophoresis, what charge will the molecule carry?

If the pH is greater than the pI in electrophoresis, what charge will the molecule carry?

• A. Negative
• B. Positive
• C. Neutral
• D. No charge

Answer: (A)

The main idea is how pH relates to net charge through the isoelectric point (pI). The pI is the pH at which a molecule has zero net charge. If the environmental pH is higher than the pI, deprotonation dominates, so acidic groups are deprotonated and the molecule gains a net negative charge. In electrophoresis, particles with negative charge move toward the positive electrode, so at pH above the pI the molecule will carry a negative charge.

The main idea is how pH relates to net charge through the isoelectric point (pI). The pI is the pH at which a molecule has zero net charge. If the environmental pH is higher than the pI, deprotonation dominates, so acidic groups are deprotonated and the molecule gains a net negative charge. In electrophoresis, particles with negative charge move toward the positive electrode, so at pH above the pI the molecule will carry a negative charge.