And now it traps that calcium and it opens up to the other side. And the calcium can now move onto this side, the other side of that membrane. And so in this way, these types of ptype ATPases can basically couple ATP. So use ATP, the energy stored in ATP, and then drive the movement of these molecules to store that energy in the existence of this electrochemical gradient. Now, this is the general diagram of how these actually work. But what exactly is the structure of the calcium ATPA?