When membrane potential equals an ion's equilibrium potential, the net diffusion of that ion is what?

When membrane potential equals an ion's equilibrium potential, the net diffusion of that ion is what?

• A. Zero
• B. Positive
• C. Negative
• D. It depends on ion

Answer: (A)

When the membrane potential matches an ion’s equilibrium potential, the forces driving that ion across the membrane cancel each other out. The equilibrium potential is the voltage at which the electrochemical driving force for that ion is zero, so there is no net flux of that ion. Ions may still shuttle back and forth through open channels, but the inward and outward movements balance, giving zero net diffusion for that ion at that moment.

When the membrane potential matches an ion’s equilibrium potential, the forces driving that ion across the membrane cancel each other out. The equilibrium potential is the voltage at which the electrochemical driving force for that ion is zero, so there is no net flux of that ion. Ions may still shuttle back and forth through open channels, but the inward and outward movements balance, giving zero net diffusion for that ion at that moment.