In this video, we're going to take a look at reactions 1 and 2 of phase A of glycolysis. Now, reaction 1 is phosphorylation. Here the enzyme Hexokinase catalyzes the phosphorylation of glucose. It uses ATP as a source of energy and phosphate. Remember that a kinase is an enzyme that transfers a phosphate group from ATP to some specified molecule. We have glucose; we're using our hexokinase. It's going to transfer a phosphate group from ATP, transforming it into ADP, and then the hydrogen that was part of glucose here is transformed into our phosphate group in the form of PO32-. So in that way, we go from glucose to glucose 6-phosphate.
Now, here, reaction 2 is isomerization. The enzyme phosphoglucoisomerase isomerizes glucose 6-phosphate to fructose 6-phosphate. They are just isomers of each other. So here, if we take a look, the number of carbons, hydrogens, oxygens, and phosphates remains the same. So we just have the changing of glucose 6-phosphate to fructose 6-phosphate through an isomerase. Remember, an isomerase is just a way of going between these different isomer forms. The same molecular formula overall, it's just different connections. Right? So that represents reactions 1 and 2 of Phase A of Glycolysis.
