So we see that ATP is an allosteric inhibitor of phosphorinase but Amp is an allosteric activator. Now actually something else also affects the activity of phosphor fructokinase and that is the PH inside that tissue. So if there is a drop in PH what that means is there's an increase in the H plus ion concentration. So why would we find a higher H plus concentration in exercising muscle cells? Well, when muscle cells are exercising, sometimes there is not enough oxygen to actually go around those cells. And so to basically continue producing those NAD plus molecules, our cells begin lactic acid fermentation.