Final answer:
FADH2 has the most potential energy compared to FAD and NAD+, due to its role in cellular respiration and its ability to store energy that is released in the synthesis of ATP.
Step-by-step explanation:
Among the molecules FAD, FADH2, and NAD+, FADH2 has the most potential energy. When considering cellular respiration and energy extraction from sugars, both NAD and FAD are crucial coenzymes that facilitate oxidation-reduction reactions. The reduced forms, such as NADH and FADH2, store energy that can be used for the synthesis of ATP. Specifically, FADH2 carries energy that contributes to the electron transport chain (ETC) in cellular respiration. It is important to note that oxidation of NADH and FADH2 releases energy for ATP production, with NADH generally contributing more to the potential energy within the electron transport chain due to its ability to transport more hydrogen ions across the mitochondrial membrane compared to FADH2. However, FADH2 still holds a considerable amount of energy, greater than its oxidized form, FAD, and NAD+, which has not yet picked up electrons or hydrogen to store energy.