Which energy-currency molecules are produced by the light-dependent reactions and used in the Calvin cycle?

• A. Only ATP is produced; NADPH is not.
• B. ATP and NADPH are produced and used in the Calvin cycle to form sugars.
• C. Only NADPH is produced; ATP is not.
• D. GTP is produced and used to synthesize proteins.

Answer: (B)

Light-dependent reactions harvest light to produce chemical energy in the form of ATP and reducing power as NADPH. These two molecules then travel to the Calvin cycle in the stroma, where ATP provides the energy needed to drive the carbon‑fixing and sugar‑synthesis steps, while NADPH donates electrons to reduce the carbon compounds as they’re converted into glyceraldehyde‑3‑phosphate. In this context, both ATP and NADPH are produced by the light reactions and used by the Calvin cycle to form sugars. GTP isn’t produced by these light reactions, and although ATP is used elsewhere, the key energy carriers here are ATP and NADPH.