What fixes carbon in photosynthesis?

Answer 1

In photosynthesis, carbon is fixed through a process known as the Calvin Cycle. This cycle takes place in the chloroplasts of plant cells and involves a series of chemical reactions. Here's a simplified explanation:

Carbon Fixation: Carbon dioxide (CO2) from the atmosphere is captured by a molecule called ribulose-1,5-bisphosphate (RuBP). This process is catalyzed by an enzyme called ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO).

Formation of 3-Phosphoglycerate (3-PGA): The CO2 is then incorporated into RuBP, resulting in the formation of 3-PGA, a 3-carbon compound.

Reduction of 3-PGA: ATP (adenosine triphosphate) and NADPH (nicotinamide adenine dinucleotide phosphate) generated during the light-dependent reactions are used to convert 3-PGA into another 3-carbon compound called glyceraldehyde-3-phosphate (G3P).

Regeneration of RuBP: Some of the G3P molecules are used to regenerate RuBP, which is crucial for sustaining the Calvin Cycle.

The fixation of carbon during photosynthesis is vital for plants to convert sunlight into energy-rich molecules like glucose, ultimately supporting their growth and providing oxygen to the atmosphere.

Answer 2

The enzyme Rubisco, or Ribulose-1,5-bisphosphate carboxylase oxygenase in the C3 pathway. In the CAM and C4 pathways, PEP Carboxylase (Phosphoenolpyruvate carboxylase) fixes carbon instead.

See related links below for more information on Rubisco and PEP Carboxylase.