In fact, in the citric acid cycle we also produce a similar molecule known as Fadh Two. Now, what exactly is the purpose of these two molecules? Well, these these molecules basically play a role in transferring or transporting our electrons from glucose into a special region on the inner mitochondrial membrane known as the electron transport chain. And what the electron transport chain does is it basically transports electrons all the way to the final electron acceptor known as oxygen and we form water as a result. And this electron transport chain also establishes an electrochemical gradient that is used to synthesize ATP molecules. And it's the ATP molecule that is used by the cell as our energy source.