So we see that this is why the cell pumps out the majority of the calcium and stores it in the endoplasm reticulum until it is actually needed. Because if the calcium is allowed to exist, if lots of calcium is allowed to exist for long periods of time in the cytoplasm, that can cause protein precipitation. And so the intrinsically low levels of cytoplasm, of cytoplasmic calcium allows the cell to actually detect even the smallest changes of increases in calcium. And we'll see, we'll talk about the actual protein called calmodulent that is used to detect this increase in concentration of calcium. Now, let's move on to fact number two about calcium that makes it such a prevalent secondary messenger molecule. So calcium ions interact strongly with proteins.