1. Carbon Fixation:
- The enzyme rubisco combines carbon dioxide (CO2) with a 5-carbon sugar called ribulose bisphosphate (RuBP).
- This forms an unstable 6-carbon compound that immediately splits into two 3-carbon molecules called 3-phosphoglycerate (3-PGA).
2. Reduction:
- 3-PGA is converted to glyceraldehyde 3-phosphate (G3P) using energy from ATP and reducing power from NADPH (both generated in the light-dependent reactions).
- This step reduces the carbon molecule, meaning it gains electrons.
3. Regeneration of RuBP:
- Most of the G3P is used to regenerate RuBP, ensuring the cycle can continue.
- A small portion of G3P exits the cycle to be used for glucose synthesis or other metabolic processes.
Summary of the Calvin Cycle:
* Purpose: To convert carbon dioxide into organic compounds, primarily glucose, using energy from the light-dependent reactions.
* Location: Stroma of the chloroplast.
* Inputs: CO2, ATP, NADPH
* Outputs: Glucose, ADP, NADP+
The Calvin Cycle is a complex series of reactions, but this simplified explanation highlights the key steps involved in converting inorganic carbon dioxide into usable organic molecules within the stroma of the chloroplast.
