Which energy carriers are produced by the light-dependent reactions and supplied to the Calvin cycle?

• A. ATP and NADPH
• B. ADP and NADP+
• C. ATP only
• D. FADH2 and NADH

Answer: (A)

Light-dependent reactions produce two key energy carriers: ATP and NADPH. In the thylakoid membranes, light energy drives electron flow from water to NADP+, forming NADPH, while the proton gradient powers ATP synthase to make ATP. These molecules then enter the Calvin cycle, where ATP provides the chemical energy to drive the cycle’s steps and NADPH supplies the reducing power needed to convert carbon dioxide into carbohydrate. NADP+ is regenerated in the process, not supplied as a product. The other options don’t fit because they either refer to molecules from cellular respiration (FADH2, NADH) or omit NADPH, or suggest ADP/NADP+ as end products rather than as forms that are regenerated or consumed in the cycle.