So we see that although NAD plus and Fad plus molecules are not a direct source of energy, they are used to actually form the energy molecules that are used by the cell, namely adenosine triphosphate or ATP molecules. Now, when these electron carrier molecules accept our electrons, they are reduced. So the fully reduced form of NAD plus is NADH, and the fully reduced form of Sad plus is Fadh too. So we see that our electrons, the high energy electrons, are accompanied by hydrogen ions. So that means when our NAD plus accepts those two electrons, it also accepts a single h plus ion to form the reduced version of our Nicotinemide adenine Dinucleotide. And when Fad plus accepts those two electrons, it accepts not one, but two h ions to form the reduced version of Flavin adenine Dinucleotide, our Fadh two.