But in l isozymes, they also respond to covalent modification via the process of phosphorylation. So when the blood glucose levels are low, the phosphorylation process of this l is I, basically makes that molecule much less active. And this means more important tissue cells. So brain cells and muscle cells can actually obtain that glucose before the liver cells actually do. And once again, to go back to our example of where we're essentially starving, we haven't eaten for weeks. We can get that sandwich because of this, because our body is able to actually regulate which cells of the body get that glucose first, so that the skeleton muscle cells, our cardiac muscle cells and the brain cells can allow us to actually get that food product.