Before it can enter the citric acid cycle, the pyruvate molecule must be prepared for that citric acid cycle. It must be activated. And that's why a process known as pyruvate decarboxylation actually takes place, pyruvate carboxylation, which is catalyzed by a large protein complex known as pyruvate dehydrogenase complex. This entire process, it releases the carbon dioxide molecule and attaches a two carbon component of the pyruvate onto a special molecule, a carrier molecule known as coenzyme A, or COA. And we formed the CETO coenzyme A complex, and this activates the two carbon fuel source of that pyruvate so that now we can actually transfer this component into the citric acid cycle. In the process.