College

Which compound is produced during carbon fixation?

A. PGA
B. G3P
C. RuBP
D. C6H12O6

Answer :

During the process of carbon fixation in photosynthesis, carbon dioxide (CO₂) is incorporated into an organic compound. This happens in the Calvin cycle, which is a series of biochemical reactions that occur in the stroma of chloroplasts in photosynthetic organisms.

Here is a step-by-step explanation of what happens during carbon fixation:

1. Start with CO₂: Carbon dioxide enters the plant cell and is absorbed in the chloroplast.

2. Reaction with RuBP: The CO₂ is then fixed by binding with a five-carbon sugar called ribulose bisphosphate (RuBP). This reaction is catalyzed by the enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase, commonly known as RuBisCO.

3. Formation of a 6-Carbon Intermediate: The combination of CO₂ with RuBP creates an unstable six-carbon intermediate that quickly splits into two molecules.

4. Production of 3-Phosphoglycerate (PGA): Each six-carbon intermediate divides into two molecules of 3-phosphoglycerate (PGA), which is a three-carbon compound.

The answer is that the compound produced during carbon fixation is PGA (3-Phosphoglycerate). This is the first stable product in the Calvin cycle.