So this irreversible reaction prepares the pyruvate for the citric acid cycle. It releases the carbon dioxide and abstracts a pair of high energy electrons that are carried by the NAD that are incent, that are ultimately used by the electron transport chain to actually generate ATP molecules, as we'll discuss in a future lecture. Now, although this net reaction looks simple, it's not actually that simple. It involves different types of enzymes and also involves different types of steps. And actually, we have four steps in pyruvate carboxylation, and three steps are actually required to form that acetyl coenzyme A complex, as we'll see in just a moment. But before we look at the details of these four steps, let's actually discuss what components we find in the pyruvate dehydrogenase complex.