Bringing carbon dioxide into the cycle
Ribulose bisphosphate (RuBP) is the five-carbon compound that accepts carbon dioxide during the first stage of the Calvin cycle.
- Rubisco (ribulose bisphosphate carboxylase) catalyses the reaction between carbon dioxide and RuBP.
- The combined product contains six carbon atoms but is not stable.
- It rapidly gives rise to two molecules of glycerate 3-phosphate (GP), each containing three carbon atoms.
+ RuBP (5C) → unstable 6C product → 2 GP (3C)
| Compound | Carbon atoms |
|---|---|
| Carbon dioxide | 1 |
| RuBP | 5 |
| Unstable product | 6 |
| GP | 3 in each molecule |