Question

What is the function of RuBisCO in the Calvin cycle?

Answer 1

Calvin cycle:

1. Following the light reactions, the Calvin cycle is the second set of metabolic processes in photosynthesis.
2. The light reactions employ photons and water to produce NADPH, oxygen, and water.
3. The NADPH may then be utilized to fuel the Calvin cycle, which generates energy by using the energy stored in ATP and NADPH during light reactions.
4. The light reactions occur in the chloroplasts, whereas the Calvin cycle occurs in the stroma and is not light-dependent.
5. The Calvin cycle produces glyceraldehyde 3-phosphate (G3P), a three-carbon sugar, by using energy to bond reactant carbon dioxide.
6. G3P is subsequently utilized to synthesize sucrose, starch, and cellulose, which are ultimately employed for energy storage and metabolism.

RuBisCO enzyme:

1. The most prevalent protein in the biosphere is ribulose bisphosphate carboxylase-oxygenase or RuBisCO.
2. During photosynthesis, it catalyzes the first stage of carbon fixation in the Calvin cycle.
3. It is the ubiquitous carbon fixation mechanism in all plants, including C3, C4, and CAM plants.
4. RuBisCO catalyzes the carboxylation of ribulose bisphosphate (RuBP), which is the major CO₂ acceptor in the C3 pathway, often known as the Calvin cycle.
5. The Calvin cycle begins with this stage.

The function of RuBisCO in the Calvin cycle:

1. RuBisCO's primary function is photosynthesis and photorespiration.
2. It catalyzes the first step in the C3 pathway or Calvin cycle, namely the carboxylation of RuBP. It leads to the production of two 3-PGA molecules.
3. RuBisCO also has an affinity for oxygen, thus it binds to some O₂ during the photorespiration process.
4. It converts RuBP to one molecule of each phosphoglycerate and phosphoglycolate.
5. Because RuBisCO has a far higher affinity for CO₂ than for O₂, photosynthesis is favored over photorespiration.