And so we actually have to undergo some other process that is exergonic to basically couple this endergonic process. Now remember one important fact about succincto enzyme A, and generally speaking, in the citric acid cycle, whenever we see a thyl ester bond between the carbon and the sulfur of the coenzyme a molecule, that bond showed in red is a very unstable high end energy bond. In fact, when we cleave this bond, that will release a certain amount of free energy. And that free energy that is released when we cleave this bond is basically used to drive the attachment of this molecule onto the GDP to form the GTP. In the process we also release that coenzyme A and form this four carbon succinate molecule that will go on to react in step six of the citric acid cycle. And this reaction is catalyzed by succinct coenzyme asynthetase.