When the light is switched off, ATP and NADPH are no longer made. What happens to the concentrations of 3-phosphoglycerate and RuBP in the Calvin cycle?
Answer and explanation
Correct answer: B. 3-phosphoglycerate rises and RuBP falls
- Step 1: Carbon fixation continues for a while, making 3-phosphoglycerate.
- Step 2: Without ATP and NADPH it cannot be converted onward, so it accumulates, and RuBP is not regenerated so it falls.
Answer
3-phosphoglycerate rises and RuBP falls.
Why not the others: Each of them rises: RuBP cannot be regenerated without ATP. 3-phosphoglycerate falls and RuBP rises: this is the opposite of what happens. Each of them stays the same: the cycle depends on light products.
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