Which statement correctly describes inputs and outputs of the light-dependent reactions?

Which statement correctly describes inputs and outputs of the light-dependent reactions?

• A. Inputs: carbon dioxide and water; Outputs: glucose.
• B. Inputs: light and water; outputs: oxygen, ATP, NADPH.
• C. Inputs: water; outputs: NADP+.
• D. Inputs: ATP and NADPH; Outputs: oxygen.

Answer: (B)

The light-dependent reactions use light energy to drive the splitting of water, release oxygen, and produce the chemical energy carriers ATP and NADPH. So the correct statement lists light and water as inputs and oxygen, ATP, and NADPH as outputs. This happens in the chloroplast’s thylakoid membranes, where light energy powers photosystems that split water, release O2, and transfer electrons to NADP+ to form NADPH, while the proton gradient drives ATP synthesis. The other options mix in products and reactants from other stages or misstate what is produced: carbon dioxide and glucose belong to the later Calvin cycle, NADP+ is not a final product here (NADPH is), and ATP and NADPH are produced, not used up, in these reactions.

The light-dependent reactions use light energy to drive the splitting of water, release oxygen, and produce the chemical energy carriers ATP and NADPH. So the correct statement lists light and water as inputs and oxygen, ATP, and NADPH as outputs. This happens in the chloroplast’s thylakoid membranes, where light energy powers photosystems that split water, release O2, and transfer electrons to NADP+ to form NADPH, while the proton gradient drives ATP synthesis. The other options mix in products and reactants from other stages or misstate what is produced: carbon dioxide and glucose belong to the later Calvin cycle, NADP+ is not a final product here (NADPH is), and ATP and NADPH are produced, not used up, in these reactions.