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NCERT lists three causes of the proton gradient across the thylakoid membrane. Which one of the following is NOT among them?

  • (a) removal of protons from the stroma by NADP reductase Your answer
  • (b) splitting of water on the lumen side Your answer
  • (c) pumping of protons by RuBisCO Correct
  • (d) transfer of protons by the hydrogen carrier during electron transport Your answer
Your answer: Correct answer: (c)
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Explanation

Why (c) is correct

RuBisCO fixes CO2 in the stroma; it does not pump protons. The three causes in NCERT are water splitting, transfer by the hydrogen carrier and NADP+ reduction.

Why the other options are wrong

  • (a) · your answer This is one of the three causes.
  • (b) · your answer This is one of the three causes.
  • (d) · your answer This is one of the three causes.
NCERT point: Together these make the lumen acidic.
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