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Which of the following are required for the dark reaction of photosynthesis?
(A) Light
(B) Chlorophyll
(C) CO2
(D) ATP
(E) NADPH
Choose the correct answer from the options given below.

  • (a) C, D and E only Correct
  • (b) D and E only Your answer
  • (c) B, C and D only Your answer
  • (d) A, B and C only Your answer
Your answer: Correct answer: (a)
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Explanation

Why (a) is correct

The dark reaction (Calvin cycle) needs CO2, ATP and NADPH. It does not use light or chlorophyll directly; it depends on light only through the ATP and NADPH made in the light reaction.

Why the other options are wrong

  • (b) · your answer CO2 is also needed: it is the substrate that is fixed.
  • (c) · your answer Chlorophyll is not used in the dark reaction, and NADPH is missing.
  • (d) · your answer Light and chlorophyll are needed for the light reaction, not the dark reaction.
NCERT point: The dark reaction is light-independent, but it stops soon after light is cut off because ATP and NADPH run out.
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