The Question is from neet-botany photosynthesis-in-higher-plants , and it was created by the author D VINOD

Question

If 36 $C{O_2}$ molecules are fixed in ${C_3}$ plant what will be?  1) The number of G3P and  2) Erythrose – 4 – phosphate formed during the dark reaction

D VINOD · Accepted Answer

## CORE INFORMATION
✓ **Answer**: B
## CONCEPT FRAMEWORK
	**Primary Concept**: Calvin Cycle ($C_3$ pathway)
	**Related Topics**: Photosynthesis, Carbon Fixation, Sugar Synthesis
	**Prerequisites**: Understanding of the steps involved in the Calvin cycle.
## SOLUTION PATHWAY
**Given Information**:
	36 $CO_2$ molecules are fixed.
**Method & Steps**:
	1. **$CO_2$ Fixation**: Each $CO_2$ molecule combines with one RuBP (ribulose-1,5-bisphosphate) to form two molecules of 3-PGA (3-phosphoglycerate).
		Reasoning: This is the first step of the Calvin cycle.
	2. **Reduction**: Each 3-PGA is reduced to G3P (glyceraldehyde-3-phosphate).
		Working: Since 36 $CO_2$ molecules produce 72 3-PGA molecules, 72 G3P molecules are initially formed.
	3. **Regeneration and Sugar Synthesis**: For every 6 $CO_2$ molecules fixed, 12 G3P are produced. Out of these 12 G3P, 10 are used to regenerate RuBP, and 2 are used for sugar synthesis.  In the $C_3$ pathway, only sucrose (made from G3P) is produced, not Erythrose-4-phosphate.
		Key Point: Erythrose-4-phosphate is formed in the Pentose Phosphate Pathway and not in the $C_3$ cycle.
	4. **Calculation**: Since 36 $CO_2$ molecules are fixed, this is equivalent to six sets of 6 $CO_2$ molecules. Thus, $6 	imes 2 = 12$ G3P molecules will be available for sugar synthesis (sucrose production), and 0 Erythrose-4-phosphate molecules will be formed.
		Result: 12 G3P and 0 Erythrose-4-phosphate
		Verification:  The Calvin cycle in $C_3$ plants primarily produces sucrose. Erythrose-4-phosphate is not a direct product of the Calvin cycle.
## OPTION ANALYSIS
[A] :x: 12 G3P is correct, but 6 Erythrose-4-phosphate is incorrect. Erythrose-4-phosphate is not produced in the $C_3$ cycle.
[B] ✓: 12 G3P and 0 Erythrose-4-phosphate. This is the correct answer as explained above.
[C] :x: 18 G3P and 6 Erythrose-4-phosphate are both incorrect.  The number of G3P is overestimated and Erythrose-4-phosphate is not a product of the $C_3$ cycle.
[D] :x: 6 G3P and 12 Erythrose-4-phosphate are both incorrect. The G3P count is underestimated, and Erythrose-4-phosphate is not produced in the $C_3$ cycle.
## LEARNING AIDS
	**Common Mistakes**:
		1. Confusing the products of the Calvin cycle with those of other metabolic pathways: Remember that Erythrose-4-phosphate is a product of the Pentose Phosphate Pathway, not the Calvin cycle.
		2. Forgetting the regeneration step: Remember that most of the G3P produced is used to regenerate RuBP.
	**Quick Tips**:
		1. For every 6 $CO_2$ fixed in the $C_3$ cycle, 2 G3P molecules are available for sugar synthesis.
		2. The $C_3$ cycle produces sucrose as the primary sugar product, not Erythrose-4-phosphate.

D VINOD · Answer

12 G3P and 6 Erythrose-4-phosphate

D VINOD · Answer

The correct Option is "12 G3P and 0 Erythrose-4-phosphate"

D VINOD · Answer

18 G3P and 6 Erythrose-4-phosphate

D VINOD · Answer

6 G3P and 12 Erythrose-4-phosphate

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