Question

If 9 ATP and 6 NADPH are utilised for carbon assimilation through Calvin cycle, what would be the ratio of erythrose 4-phosphate, xylulose 5-phosphate and ribulose 5-phosphate during regeneration phase?

• A. 3 : 1 : 2
• B. 2 : 2 : 1
• C. 2 : 3 : 1
• D. 1 : 2 : 3

Answer 1

The correct option is D 1 : 2 : 3

Normally 6 cycles of Calvin cycle utilise 18 ATP and 12 NADPH to produce 6 mol. of RuBP and carbohydrates.

In this following reaction produce erythrose- 4- phosphate, xylulose 5- phosphate and ribulose 5 phosphates.

1. 2 mol. of fructose-6- phosphate with two mol. of 3- phosphoglyceraldehyde to produce 2 mol. of erythrose-4- phosphate and 2 mol. of xylulose-5 -phosphate.

2. 2 mol. of ribose-5- phosphate are converted to 2 mol. ribulose-5-phosphate.

3. 2 mol. of sedoheptulose-7-phosphate with 2 mol. of 3- phosphoglyceraldehyde produce 2 mol. of ribose-5 phosphate and xylulose-5- phosphate.

4. 4 mol. of Xylulose-5- phosphate are isomerised to 4 mol. of ribulose-5- phosphate.

Therefore, In total 2 mol. of erythrose-4-phosphate, 4 mol. of xylulose-5-phosphate, 6 mol. of ribulose-5-phosphate are produced.

If 9 ATP and 6 NADPH are utilised, In total 1 mol. of erythrose-4-phosphate, 2 mol. of xylulose-5-phosphate, 3 mol. of ribulose-5-phosphate are produced.

Hence, the correct answer is '1:2:3'.