The ATP and NADPH produced during light-dependent reactions are used in which process?

• A. Light-independent Reactions
• B. Light-Dependent Reactions
• C. Photosystems
• D. ATP Synthase

Answer: (A)

ATP and NADPH from the light reactions carry the energy and reducing power needed to build carbohydrates in the next stage of photosynthesis. In the Calvin cycle, these molecules drive the fixation of carbon dioxide into sugars. ATP provides the energy to power the biochemical steps, while NADPH donates electrons to reduce carbon compounds, enabling their conversion into glyceraldehyde-3-phosphate and ultimately glucose. This stage happens in the stroma and does not require light directly, which is why it’s called light-independent even though it relies on the products of light reactions. Photosystems and ATP synthase are part of the light-dependent processes that generate these molecules, not the stage that uses them to fix carbon.