Question

Which part of the light-independent reactions would be affected if a cell could not produce the enzyme RuBisCO?

a) Formation of G3P
b) Reduction of PGA
c) Regeneration of RuBP
d) Cleavage of PGA

Answer 1

The fixation stage of the light-independent reactions would be affected if a cell could not produce RuBisCO, as this enzyme catalyzes the attachment of CO₂ to RuBP, which is essential for the Calvin cycle to proceed. Hence, the correct answer is option (a).

Step-by-step explanation:

If a cell could not produce the enzyme RuBisCO, the part of the light-independent reactions that would be affected is the fixation of carbon dioxide. RuBisCO, the enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase, catalyzes the critical first step where CO₂ is attached to ribulose bisphosphate (RuBP).

This reaction results in the production of two molecules of 3-phosphoglycerate (3-PGA), a precursor for the production of glucose. Without RuBisCO, the Calvin cycle cannot proceed, as the carbon fixation stage is crucial for the synthesis of organic compounds from CO₂.

Hence, the Calvin cycle would be halted at the initial stage, and none of the subsequent reactions, such as the reduction to form G3P or the regeneration of RuBP, would occur.