When that takes place, this entire section basically opens up. And now these calcium ions can once again go into the transmembrane domain and the cycle can basically restart itself. So we see that what the ptype Atpas does, what the calcium Atpas does is it moves two of these calcium ions against the electrochemical gradient from a low to a high concentration. And the way that it does this is by using the energy that is stored in these ATP molecules. So that's exactly why these membrane pumps are energy transducers. They essentially take one form of energy.