Question

Observe the given figure. Identify the different stages labelled with alphabets by selecting the correct option

• A. A-Carboxylation, B-Regeneration, C-Reduction
• B. A-Reduction, B-Decarboxylation, C-Regeneration
• C. A-Carboxylation, B-Reduction, C-Regeneration
• D. A-Reduction, B-Carboxylation, C-Regeneration

Answer 1

The Correct Option is C

The given diagram represents the Calvin cycle, which is a part of photosynthesis occurring in the chloroplasts of plant cells. The cycle has three main stages: Carboxylation, Reduction, and Regeneration.

1. Carboxylation (Stage A):

In this initial stage, carbon dioxide (CO₂) is fixed into an organic molecule. Ribulose 1,5-bisphosphate (RuBP) reacts with CO₂ to form 3-phosphoglycerate. This reaction is catalyzed by the enzyme RuBisCO. Therefore, Stage A is the Carboxylation phase.

1. Reduction (Stage B):

During this stage, ATP and NADPH (generated in the light-dependent reactions) are used to convert 3-phosphoglycerate into glyceraldehyde-3-phosphate, a type of triose phosphate. This is an energy-investment phase where the reduction of 3-phosphoglycerate occurs, hence Stage B is the Reduction phase.

1. Regeneration (Stage C):

This phase involves the regeneration of RuBP from triose phosphates, allowing the cycle to continue. ATP is used to regenerate RuBP, ensuring that the cycle can perpetuate. Hence, Stage C is the Regeneration phase.

Thus, the correct sequence is:

Correct Answer: A-Carboxylation, B-Reduction, C-Regeneration