For instance, if, let's say, a cell needs to decrease the number of protein channels found in the cell membrane, it has to be able to remove those protein channels and then digest those protein channels. And so inside the cells, we have these digestive enzymes in the same way that we have digestive enzymes inside our small intestine as well as inside our stomach. And these digestive enzymes are proteases. They are used to break down and recycle the proteins found inside our cells. And finally, as we'll discuss in much more detail in the future, these proteases are also actually used in proteolytic cleavage and that is used to activate or sometimes deactivate important biological pathways and biological molecules. So as we'll see in the future lecture, these different types of digestive enzymes are actually themselves activated by other proteases.