Question

The purpose of phosphoribulokinase in the Calvin Cycle is to:

a) Catalyze the conversion of ribulose-1,5-bisphosphate (RuBP) into two molecules of 3-phosphoglycerate (3-PGA).
b) Facilitate the regeneration of ribulose-1,5-bisphosphate (RuBP) from 3-phosphoglycerate (3-PGA).
c) Convert ATP into ADP to provide energy for the Calvin Cycle reactions.
d) Assist in the fixation of carbon dioxide to form a stable intermediate compound.

Answer 1

Phosphoribulokinase in the Calvin Cycle aids in regenerating RuBP from 3-PGA, using ATP in the process.

Step-by-step explanation:

The purpose of phosphoribulokinase in the Calvin Cycle is to facilitate the regeneration of ribulose-1,5-bisphosphate (RuBP) from 3-phosphoglycerate (3-PGA). This enzyme uses the energy from ATP to phosphorylate 3-PGA during the regeneration stage of the Calvin cycle, ultimately leading to the production of RuBP, which is then ready to react with more incoming CO₂. It's important to understand that RuBP is essential for carbon fixation in the Calvin cycle, where it serves as the molecule that reacts with CO₂ to form 3-PGA in a process catalyzed by ribulose bisphosphate carboxylase (RuBisCO).