In the second step three B, the oxylote undergoes a decreboxylation step in which we release a carbon dioxide and we produce a five carbon molecule alpha ketoglutrate. Now, let's imagine inside our cell we want to produce ATP molecules. So we have a low energy charge value, we don't have enough ATP and so we want to make sure, or the cell wants to make sure that the citric acid cycle takes place at a high rate. And what the cell does is to make sure the rate is high is it stimulates the isocitrate dehydrogenase. So the isocitrate dehydrogenase, being an allosteric enzyme, contains allosteric regulatory sites and an allosteric activator molecule, ADP adenosine diphostate, will go on and bind onto special location on the enzyme isocitrate dehydrogenase. And once it binds, it increases its affinity for the substrate molecule isocitrate.