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Multiple Choice
Why is the regeneration step of the Calvin cycle essential?
A
It releases oxygen as a byproduct of photosynthesis.
B
It replenishes ribulose-1,5-bisphosphate (RuBP), allowing the cycle to continue fixing carbon dioxide.
C
It converts glucose directly into pyruvate for cellular respiration.
D
It produces ATP required for the light-dependent reactions.
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 responsible for fixing carbon dioxide into organic molecules, ultimately producing glucose.
Identify the role of ribulose-1,5-bisphosphate (RuBP): RuBP is a 5-carbon sugar that acts as a substrate for the enzyme RuBisCO, which catalyzes the fixation of carbon dioxide into an organic molecule. Without RuBP, the cycle cannot proceed.
Explain the regeneration step: The regeneration step of the Calvin cycle ensures that RuBP is replenished. This step involves a series of reactions where intermediate molecules are rearranged and converted back into RuBP using ATP.
Highlight why regeneration is essential: Without the regeneration of RuBP, the Calvin cycle would halt, preventing the fixation of additional carbon dioxide and the production of glucose. This step is critical for the continuity of the cycle.
Clarify misconceptions: The regeneration step does not release oxygen, produce ATP for light-dependent reactions, or convert glucose into pyruvate. Its sole purpose is to replenish RuBP to sustain the Calvin cycle.