Question

In three Calvin cycles, gross number of PGAL molecules produced at the cost of ATP and NADPH${}_2$ is

• A. 3PGAL, 3ATP, 3NADPH${}_2$
• B. 6PGAL, 6ATP, 6NADPH${}_2$
• C. 18PGAL, 18ATP, 18NADPH${}_2$
• D. 9PGAL, 9ATP, 9NADPH${}_2$

Answer 1

Answer: (B)

6PGAL, 6ATP, 6NADPH${}_2$

ATP and NADPH are used during the regeneration phase of the Calvin cycle.

• During regeneration 12 mol. of 3- phosphoglycerate, phosphorylation by 12 mol. of ATP to form 12 mol. of 1,3 - bisphosphoglycerate in presence of enzyme phosphoglycerate kinase. The molecules of ATP get converted to ADP.
• 12 mol. of 1,3 - bisphosphoglycerate are reduced to 12 mol. of 3- phosphoglyceraldehyde in presence of coenzyme NADPH. The reaction is catalyzed by the enzyme triosephosphate dehydrogenase. Inorganic phosphate is released.

In 6 calvin cycle, 12 mol. of PGAL are produced at the cost of 12 mol. of ATP and 12 mol. of NADPH${}_2$.

In 3 calvin cycle, 6 mol. of PGAL are produced at the cost of 6mol. of ATP and 6mol. of NADPH${}_2$.

Hence, the correct answer is '6PGAL, 6 ATP, 6 NADPH${}_2$'.