Explain how the regulation of the Calvin cycle by the redox state of the plastoquinone pool influences the activity of the enzyme fructose‑1,6‑bisphosphatase. Include in your explanation the role of NADPH and ATP.
Answer
The reduced plastoquinone pool generates NADPH and ATP, which phosphorylate and activate fructose‑1,6‑bisphosphatase, thus enhancing the Calvin cycle.
Step-by-step solution
- Understand that a reduced plastoquinone pool leads to a higher NADPH/NADP⁺ ratio and ATP production via ATP synthase.
- Recognize that fructose‑1,6‑bisphosphatase is regulated by phosphorylation; the enzyme is active when phosphorylated and inactive when dephosphorylated.
- Link the availability of NADPH and ATP to the phosphorylation state: sufficient NADPH and ATP allow the kinase to phosphorylate the enzyme.
- Thus a reduced plastoquinone pool boosts NADPH and ATP, leading to phosphorylation and activation of fructose‑1,6‑bisphosphatase, which promotes the Calvin cycle.
Common mistake: Overlooking the link between NADPH/ATP and enzyme phosphorylation
Concept tested: Redox regulation of Calvin cycle enzymes
Published · How this solution was prepared and checked
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