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Which of the following combinations is required for chemiosmosis?

  • (a) membrane, proton pump, proton gradient, ATP synthase Correct
  • (b) membrane, proton pump, proton gradient, NADP synthase Your answer
  • (c) proton pump, electron gradient, ATP synthase Your answer
  • (d) proton pump, electron gradient, NADP synthase Your answer
Your answer: Correct answer: (a)
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Explanation

Why (a) is correct

Chemiosmosis needs a membrane, a proton pump, a proton gradient across the membrane and ATP synthase. Protons flow back through ATP synthase, and this drives ATP formation.

Why the other options are wrong

  • (b) · your answer ATP synthase, not "NADP synthase", uses the proton gradient; NADPH is made by NADP reductase.
  • (c) · your answer Chemiosmosis needs a proton gradient, not an electron gradient, and a membrane.
  • (d) · your answer Both the gradient and the enzyme are wrong; it is a proton gradient and ATP synthase.
NCERT point: In chloroplasts, protons build up in the thylakoid lumen and flow out to the stroma through the CF0-CF1 ATP synthase.
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