BRAINCAKEThe Calvin Cycle
The Calvin cycle is the series of enzyme-controlled reactions in the stroma that fixes carbon dioxide into carbohydrate.
1. Carbon fixation: CO2 combines with ribulose bisphosphate (RuBP), a 5-carbon compound, catalysed by RUBISCO. The unstable 6-carbon product immediately splits into two molecules of glycerate 3-phosphate (GP), a 3-carbon compound.
2. Reduction: GP is reduced to glyceraldehyde 3-phosphate (GALP), a 3-carbon sugar phosphate (triose phosphate), using hydrogen from reduced NADP and energy from ATP. The NADP and ADP return to the thylakoids to be reused.
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Key terms in this lesson
- nadp
- A coenzyme that acts as a hydrogen acceptor in the light-dependent reactions of photosynthesis, becoming reduced NADP when it accepts hydrogen.
- rubisco
- The enzyme that catalyses the fixation of carbon dioxide by combining it with RuBP in the Calvin cycle, and can also catalyse a competing reaction with oxygen (photorespiration).
More in Photosynthesis
- The Light-Dependent Reactions
- Cyclic Photophosphorylation
- Non-Cyclic Photophosphorylation
- The Light-Independent Stage
- The Products of Photosynthesis
- C4 Plants
- Rubisco
- Limiting Factors of Photosynthesis
All 20 lessons in Photosynthesis · All Edexcel A-level Biology topics