What is the primary difference between membrane potential and electrochemical potential?

• A. Membrane potential is static, while electrochemical potential is dynamic.
• B. Membrane potential only considers electrical gradients, while electrochemical potential only considers concentration gradients.
• C. Membrane potential is the sum of concentration and electrical gradients, while electrochemical potential is their difference.
• D. Membrane potential is the difference between concentration and electrical gradients, while electrochemical potential is their sum.

Answer: (D)