Which compound is produced during regeneration? A. 3-PGA B. G3P C. RuBP D. rubisco
The Correct Answer and Explanation is:
The correct answer is C. RuBP.
In the Calvin Cycle of photosynthesis, the regeneration phase is the last part of the cycle, following the carbon fixation and reduction phases. This phase primarily focuses on regenerating the molecule ribulose bisphosphate (RuBP), which is essential for the cycle to continue. RuBP is the molecule that reacts with carbon dioxide during the carbon fixation phase, catalyzed by the enzyme rubisco. Here’s a breakdown of how the regeneration phase works:
- Starting with G3P: In the reduction phase, three molecules of 3-phosphoglycerate (3-PGA) are converted into glyceraldehyde-3-phosphate (G3P), a three-carbon sugar. Some of the G3P molecules exit the cycle and are used to form glucose and other carbohydrates, while the remaining G3P molecules stay in the cycle.
- Regeneration of RuBP: The remaining G3P molecules undergo a series of enzyme-mediated reactions that reorganize their carbon structure to regenerate RuBP. Specifically, for every three molecules of G3P, five molecules of carbon are rearranged to regenerate three molecules of RuBP. This allows the cycle to continue, as RuBP is required to capture CO2 and start the cycle again.
- Energy Use: Regenerating RuBP requires ATP, which provides the energy for the rearrangement of carbon atoms. This process ensures that the cycle can continue without running out of RuBP.
In summary, the regeneration phase restores RuBP to the cycle, ensuring that the Calvin Cycle can continuously fix carbon dioxide and produce sugars. This regeneration of RuBP is vital for the overall process of photosynthesis.
