Question

The compound formed as net gain in carbon assimilation is

• A. 3-C DHAP of third CO${}_2$- fixation
• B. GAP of second CO${}_2$ fixation
• C. Erythrose 4-phosphate reacting with DiHAP
• D. RuBP

Answer 1

Answer: (A)

3-C DHAP of third CO${}_2$- fixation

During regeneration 12 mol. of 3- phosphoglycerate are phosphorylated by 12 mol. of ATP to form 12 mol. of 1,3 - bisphosphoglycerate in presence of enzyme phosphoglycerol 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.

3- phosphoglyceraldehyde is isomerized to dihydroxyacetone phosphate in presence of enzyme Triose Phosphatase isomerase.

Hence, the correct answer is '3-C DiHAP of third CO${}_2$- fixation'.