1. Stage 3 - The Calvin Cycle and Carbon Fixation
Melvin Calvin won the Novel Prize in Chemistry in 1961 for his work in discovering this pathway
He used a radioactive isotope of carbon as a tracer to discover the sequence of reactions that results in carbon fixation

2. Carbon fixation is the process of forming high-energy molecules from CO2.
These reactions are light independent
The Calvin cycle occurs in the stroma
The cycle uses materials generated by the light dependent reactions - ATP molecules and high energy electrons carried by NADPH

3. 1. Fixing Carbon Dioxide
Carbon dioxide is bonded to a molecule of ribulose bisphosphate (RuBP) - a 5-carbon compound which exists in the stroma
The new 6-carbon compound is very unstable
Immediately breaks down into two identical 3-carbon molecules
CO2 + RuBP  unstable C6  2 C3

4. 2. Energy Transfer
3 ATP and 2 NADPH are used for EVERY CO2 that enters the cycle
Each turn of the Calvin cycle produces 2 high-energy C3 molecules

5. 3. Replacing RuBP
Most of the C3 molecules are used to generate more RuBP in the stroma
The Calvin Cycle must be completed six times in order to synthesize one molecule of glucose
Each cycle produces 2 C3 molecules,  at the end of 6 cycles, there are 12 C3 molecules. 10 of these are used to regenerate RuBP, and 2 are used to make glucose.

9. Summary of reactants and products
1. Light-dependent:
Reactants:
Products:
Carbon-fixation:

11. Why do plants require H2O?
H2O undergoes photolysis and provides electrons to PSII

12. Why do plants require CO2?
To be “fixed” into C3 and glucose molecules by the Calvin cycle

13. When and where is O2 produced?
When water undergoes photolysis, O2 is released. Photolysis occurs in the lumen.

14. What happens to the hydrogen of H2O?
Contributes to the electrochemical gradient that drives chemiosmosis

15. 18 ATP molecules and 12 NADPH molecules
How many ATP and NADPH are required to produce one molecule of glucose?
18 ATP molecules and 12 NADPH molecules