A cell membrane has a transmembrane potential of -70 mV and a chemical gradient favoring the influx of Na+ ions. Why is it important to consider both gradients for Na+ diffusion?

• A. Only the chemical gradient affects Na+ ion diffusion.
• B. Only the electrical gradient affects Na+ ion diffusion.
• C. Both gradients determine the direction and rate of Na+ ion diffusion.
• D. Neither gradient affects Na+ ion diffusion.

Answer: (C)