Well, a fuel molecule is a molecule that contains carbon atoms and can be oxidized to obtain these electrons, which then can be used, as we'll see, in just a moment, to form ATP molecules. Now, the citric acid cycle also functions to provide the building blocks needed to form biological molecules such as nucleotide bases, amino acids, glucose molecules, porphyrin molecules and so forth. And we'll discuss all this in much more detail in lectures to come. But let's actually generalize what the steps of the citric acid cycle actually are. So the Cecil Coenzyme A donates a small component of that molecule, a two carbon component, the Cecil group, into the citric acid cycle. And this is what is shown here.