So to close the circuit, we need this membrane. And so these H plus ions travel from the anode to the cathode. And when they reach this position, they react with the oxygen and the electrons forming water. Now, this water needs to be released somewhere because if the water remains, there's a build up of water and now cell would eventually stop functioning. So this water leaves through some outside pump and is stored somewhere else. Now, notice, the same way we need to allow H two molecules inside our ano, we need to allow o two molecules inside our capital.