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. Now the second important difference is the molecule citrate. So citrate, as we'll see in just a moment, just like ATP molecules is another example of an allosteric inhibitor to phosphor fructosekinase. So let's suppose in our liver cells we have a high oxygen content but we don't have many ATP molecules.