Because if we have too many glucose in the blood, that can be toxic to our bodies. So let's suppose we just ingest a meal that is rich in carbohydrates and so the concentration of ATP in our blood essentially increases. And it's the job of the liver cells to basically uptake all that glucose to bring the blood level glucose back to normal. Now, what does the cell actually do with the glucose? Well, it can form ACP molecules, it can form many different types of building blocks, it can form glycogen. And what that means is in these situations the phosphor fructokinase must be activated by some type of powerful activator molecule to actually uptake all those glucose molecules and convert those glucose molecules into these different types of things.