But there are many important differences. Difference number one, in skeleton muscle cells the PH actually affects the activity of phosphop fructokinase. So in our discussion previously we said that a low PH or a very acidic environment basically inactivates inhibits phosphoruxokinase in skeletal muscle cells and that's because in skeletal muscle cells as we exercise there can be a build up in lactic acid. But in liver cells there is usually no buildup in lactic acid. And that's partly because the liver cells actually are responsible for breaking down that lactic acid into glucose molecules. And that's exactly why the phosphorptokinase is not affected by the PH in liver cells.