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Accumualtion of DHAP in the stroma of th...

Accumualtion of DHAP in the stroma of the chloroplast slow down calvin cycle reactions is an example for

A

Un catalysed biochmical reaction

B

Compititive inhibition

C

Feed back inhibition

D

Both 2 and 3

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To solve the question regarding the accumulation of DHAP (Dihydroxyacetone phosphate) in the stroma of the chloroplast and its effect on the Calvin cycle, we can follow these steps: ### Step-by-Step Solution: 1. **Understanding DHAP and Its Role**: - DHAP is an intermediate in the Calvin cycle, which is essential for the fixation of carbon dioxide into organic compounds in plants. 2. **Identifying the Problem**: - The accumulation of DHAP indicates that there is a disruption in the Calvin cycle. Specifically, it suggests that the cycle is not proceeding to produce the end products, such as glucose. 3. **Mechanism of Accumulation**: - When DHAP accumulates, it implies that the conversion of DHAP into other intermediates (like ribulose bisphosphate, or RuBP) is not occurring efficiently. This can be due to a lack of necessary substrates or enzymes. 4. **Exploring Possible Mechanisms**: - The question provides several options: uncatalyzed biochemical reaction, competitive inhibition, and feedback inhibition. - Uncatalyzed reactions do not apply here as DHAP accumulation is not due to the absence of a catalyst. - Competitive inhibition involves an inhibitor blocking the substrate from binding to the enzyme, which does not directly explain the accumulation of DHAP. 5. **Identifying Feedback Inhibition**: - Feedback inhibition is a regulatory mechanism where the accumulation of an end product inhibits an earlier step in the metabolic pathway. In this case, the accumulation of DHAP serves as a signal that the Calvin cycle is not producing sufficient end products, leading to a slowdown in the cycle. 6. **Conclusion**: - Therefore, the accumulation of DHAP in the stroma of the chloroplast slowing down the Calvin cycle is an example of feedback inhibition. ### Final Answer: The accumulation of DHAP in the stroma of the chloroplast slowing down Calvin cycle reactions is an example of **Feedback Inhibition**. ---
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