Dark reaction.

Light independent reaction (dark reactions)

It is a sequence of events which was discovered by a man called Calvin Benson in 1946–53. Therefore it is called the Calvin Benson cycle.

Takes place in the stroma of the chloroplast. It does not depend on light but uses ATP and NADPH (the reduced Nicotinamide Adenine Diphosphate) to reduce CO₂ to form sugar.

The Calvin cycle functions as a sugar factory within the chloroplast. It uses inputs like CO₂, ATP, and NADPH to construct energy-rich sugar molecules.

Stages of Calvin cycle

1. Carbon dioxide fixation (acceptance of carbon dioxide).
2. Energy consumption.
3. Release of one molecule of G3P (glyceraldehyde-3-phosphate).
4. Regeneration of RuBP (ribulose-1,5-bisphosphate).