Location: Takes place in the stroma of the chloroplast.

Phases of the Calvin Cycle:
1. Carbon Fixation:
2. Reduction Phase:
3. Regeneration of RuBP:
Key Enzyme:
- RuBisCO is the primary enzyme, acting as both a carboxylase and an oxygenase.
- Can bind to CO₂ (carboxylation) or O₂ (oxygenation), the latter leading to photorespiration, which reduces efficiency.
Energy Requirement:
- For each full turn of the cycle (producing 1 G3P):
- To produce one glucose molecule, the cycle must run twice, requiring:
Products:
- G3P is the direct product, which can be used to form glucose and other carbohydrates.
Photorespiration Issue:
- Occurs when RuBisCO fixes O₂ instead of CO₂, leading to wasteful energy loss.
- More likely in hot, dry climates when stomata close to conserve water.
Adaptations:
- C4 and CAM plants have evolved mechanisms to minimize photorespiration and improve efficiency, which will be explored further.