AQA A-Level Biology 2025/6

Biology • A-Level

Question 1 of 40

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In the light‑dependent reactions of photosynthesis, ATP and reduced NADP (NADPH) are produced. Which statement best describes how these molecules are used in the subsequent Calvin‑Benson cycle?

Hint: Remember what each molecule carries: ATP = energy, NADPH = electrons/reducing power.

NADPH provides the energy for the carboxylation of ribulose‑1,5‑bisphosphate, while ATP reduces 3‑phosphoglycerate. ATP provides the energy required for regeneration of ribulose‑1,5‑bisphosphate, while NADPH supplies the electrons needed to reduce 3‑phosphoglycerate to glyceraldehyde‑3‑phosphate. ATP supplies the carbon atoms for the synthesis of ribulose‑1,5‑bisphosphate, and NADPH transports oxygen to the stroma. Both ATP and NADPH are directly incorporated into the carbon backbone of the glucose molecule formed.

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