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Multiple Choice
Which of the following best describes what occurs during the regeneration stage of the Calvin cycle?
A
Carbon dioxide is fixed to form 3-phosphoglycerate (3-PGA).
B
ATP and NADPH are produced from light energy.
C
Ribulose-1,5-bisphosphate (RuBP) is regenerated from some of the G3P molecules, allowing the cycle to continue.
D
Glucose is directly synthesized from G3P molecules.
Verified step by step guidance
1
Understand the Calvin cycle: The Calvin cycle is a series of biochemical reactions that occur in the stroma of chloroplasts during photosynthesis. It is divided into three main stages: carbon fixation, reduction, and regeneration.
Focus on the regeneration stage: During the regeneration stage, some of the glyceraldehyde-3-phosphate (G3P) molecules produced in the reduction stage are used to regenerate ribulose-1,5-bisphosphate (RuBP), which is essential for the cycle to continue.
Recognize the role of ATP: ATP is used as an energy source during the regeneration stage to convert G3P into RuBP. This ensures that RuBP is available to accept new carbon dioxide molecules in the next cycle.
Eliminate incorrect options: The regeneration stage does not involve the fixation of carbon dioxide (this occurs in the carbon fixation stage), the production of ATP and NADPH (this occurs in the light-dependent reactions), or the direct synthesis of glucose (glucose synthesis involves multiple steps beyond the Calvin cycle).
Conclude the correct description: The best description of the regeneration stage is that ribulose-1,5-bisphosphate (RuBP) is regenerated from some of the G3P molecules, allowing the Calvin cycle to continue.