Final answer:
The true statement regarding NADPH and NADH is that they are used in separate biochemical pathways within cells, with NADPH being central to photosynthesis and NADH to cellular respiration.
Step-by-step explanation:
The correct statement regarding NADPH and NADH is A. NADPH and NADH are used in separate biochemical pathways in cells. NADPH is primarily involved in the photosynthesis process in plants, whereas NADH plays a crucial role in the cellular respiration process in both animal and plant cells.
NADPH is produced during the light-dependent reactions of photosynthesis and carries energy and electrons for the reduction of carbon dioxide in the Calvin cycle. It loses a hydrogen atom to become NADP+ when it releases the stored energy. NADH, on the other hand, is generated primarily during the citric acid cycle in the mitochondria of cells. It transfers electrons to the electron transport chain to produce ATP, a key energy currency in the cell.
Furthermore, while both molecules are involved in electron transfer, they do not deliver electrons to the same set of enzymes and do not interconvert by simple loss or gain of a phosphate group.