So they use ATP and ANP molecules so let's suppose we have a high energy charge in the cell and what that means is we have a high ratio of ATP to amp. Remember, energy charge simply means the ratio of ATP to amp. Now if we're resting this is basically what we're going to have. We're going to have too many ATP molecules. And so what that means is we don't want to produce any more ATP molecules. We have plenty of ATP molecules to go around and so phosphorutokinase will be inhibited by that large concentration of ATP and ATP acts as an allosteric inhibitor.