Question

Calvin Cycle: Purpose of RubisCO

a) To produce glucose
b) To fix carbon dioxide
c) To generate ATP
d) To synthesize water

Answer 1

RuBisCO's purpose in the Calvin Cycle is to catalyze the carbon fixation step, where CO₂ is attached to RuBP which eventually leads to the production of G3P, used in glucose synthesis and to regenerate RuBP. Therefore, correct option is b.

Step-by-step explanation:

Purpose of RubisCO in the Calvin Cycle

The enzyme RuBisCO plays a crucial role in the Calvin Cycle, which is a series of biochemical redox reactions that take place in the stroma of chloroplasts in photosynthetic organisms. The main function of RuBisCO is to catalyze the first step of the Calvin Cycle known as carbon fixation.

During this step, RuBisCO facilitates the attachment of carbon dioxide (CO₂) to ribulose bisphosphate (RuBP), eventually leading to the production of 3-phosphoglycerate (3-PGA).

As part of the cycle's subsequent stages, the 3-PGA is then reduced to glyceraldehyde-3-phosphate (G3P), using energy from ATP and electrons from NADPH, both of which are produced in the light-dependent reactions of photosynthesis.

Some of the G3P is used to build glucose and other carbohydrates, while the rest is utilized to regenerate RuBP, thus preparing the system for another round of carbon fixation. Therefore, the correct answer to the purpose of RuBisCO in the Calvin Cycle is b) To fix carbon dioxide.