So in the second step, the enzyme phosphoglucose isomerase transforms the glucose which is an aldos, it contains an aldehyde group into a fructose, which is a keto that contains this ketone group. So this is a ketone and this is an aldehyde. So we see that in step two of stage one, the entire point is to transform an aldos into a keto. Now let's move on to step three of stage one. So it's basically not enough to add that phosphoryl group, we have to add a second phosphoryl group because remember, the entire point of step or stage one is to destabilize that glucose as much as we can. And so to further destabilize the structure of glucose to increase its energy and make it much more reactive, in step three of stage one, we have an enzyme known as phosphor fructosekinase PFK that catalyzes the addition of yet another phosphoryl group onto a carbon of that fructose.