In step four, we take the alpha key to gluterate produced in step three, and we basically kick off a carbon dioxide molecule and replace it with coenzyme A to form submit coenzyme A, we also oxidize the alpha ketoglutrate and reduce the NAD plus into NADH. And here's our carbon dioxide molecule. So alpha ketoglutrade catalyzes the second oxidative decarboxylation step. Now, if we have a high energy charge value inside our cells, so we have plenty of ATP molecules to go around and we don't want to produce any more ATP molecules, we see that ATP, as well as these two molecules produced, will act as allosteric inhibitors. So ATP, as well as succinctoenzyme A and NADH will basically act as allosteric inhibitors, binding them to special regulatory sites of this alpha keyoglutrade dehydrogenous enzyme and that will inhibit its activity. And so when we have plenty of ATP, the rate of the citric acid cycle is basically decreased.