Before we can actually take the glucose and attach the glucose onto that growing glycogen polymer, we have to make that glucose a reactive molecule, because glucose by itself, and more specifically, glucose one phosphate, is not reactive enough, it's not high in energy to basically attach itself onto that glycogen chain. What we have to do before anything is actually activate that glucose molecule. And by activating, I mean we have to make it more reactive, we have to increase its energy. So glucose by itself is not active enough to attach on to that growing glycogen chain. Therefore, the first step in this process is to actually transform glucose into a more reactive and high energy form. And that's exactly what happens in this step and this step here.