And then the membrane channels use these gradients to basically move these molecules spontaneously from one side to the other side down that electrochemical gradient. So we said a moment ago that we have two types of pumps. We have ATP Aces and we also have second air transporter. So really briefly, what exactly is a secondary transporter? Well, a secondary transporter is a pump that doesn't use ATP directly. What it does instead is it uses the electrochemical gradient of one molecule to move a second molecule against its electrochemical gradient.