So I was watching a video about Gibbs-Donnan equilibrium () On one side of the semipermeable membrane, there is a solution of potassium ions and impermeable protein ion (negative 1 charge). On the other side there is potassium chloride. It said that after the electrical and chemical gradients are satisfied and the system reaches equilibrium, there is no net charge on either side, since the no. of moles of negatively charged ions on each side is equal to the no. of moles of positively charged ions. Then how is there are potential difference across the membrane? I'm thinking that it might be because the protein ions adsorb on to the membrane surface, imparting a charge to it. Is that true?