As these guys go across the membrane, there's a build up of positive charge. And this slows down the movement because positive charge and positive charge repel. And so eventually, these guys will stop moving this way. And that means now we can talk about another gradient called the electrical gradient. Now, the electrical gradient is due to charge and not number. So the more charge there is here, the more our electrical gradient will play a role in dictating in which direction our molecule moves.