Question

How does carbon fixation work?

Answer 1

Carbon fixation:

1. Carbon fixation is the process by which plants fix inorganic carbon to produce organic compounds.
2. It is the light-independent or dark reaction of photosynthesis.
3. It utilizes ATP and NADPH produced in the light reaction of photosynthesis.
4. Calvin cycle or C3 cycle is the common pathway of photosynthesis in all plants.
5. The Calvin cycle has three main steps, carboxylation, reduction, and regeneration.
6. RuBP is carboxylated to produce PGA.
7. PGA is further reduced to produce G3P. ATP and NADPH are utilized in this step.
8. G3P is utilized by plant cells to produce sugar or starch.
9. Six turns of the C3 cycle are required to produce one molecule of glucose.
10. In each turn, 3 ATP and 2 NADPH molecules are utilized.

RuBisco:

1. Ribulose-1,5-bisphosphate carboxylase/oxygenase, better known by the name Rubisco, is the key enzyme responsible for photosynthetic and chemoautotrophic carbon fixation and oxygen metabolism.
2. RuBisCO catalyzes the first step of carbon fixation during photosynthesis.
3. It catalyzes the carboxylation of RuBP to produce two molecules of 3-PGA.
4. When O₂ binds to RuBisCO, RuBP is converted to one molecule each of phosphoglycerate and phosphoglycolate instead of 3-PGA.
5. The process is called photorespiration.