So we essentially have our first step of glycogen breakdown. So on the left side we have the reactant, the glycogen molecule that contains, let's suppose, N number of glucose molecules. And to simplify the diagram of only drawn two of these glucose molecules. Now, this is the terminal glucose molecule that contains the free hydroxyl group on carbon number four of the glucose. And so this is the alpha one four glycocitic bond that will be cleaved by the glycogen phosphorlase. Now, the other reactant of this particular reaction is the orthophosphate.