1. The Dark Side
of Photosynthesis
In stroma
In 3 stages

2. Dark Reaction/ Calvin Cycle
of Photosynthesis
In stroma
In 3 stages

3. Dark Reaction/ Calvin Cycle
uses ATP and NADPH (from light reaction) to convert CO2 to sugar

4. Dark Reaction/ Calvin Cycle
Phase 1: Carbon Fixation
Phase 2: Reduction
Phase 3: Regeneration of RuBP

5. We are in the STROMA

6. We are in the STROMA

7. phase 1 Carbon Fixation --> X3
CO2 attaches to a 5C sugar Ribulose Biphosphate (RuBP) via. Rubisco:
P-C-C-C-C-C-C-P
Rubisco (RuBP carboxylase) = enzyme

8. phase 1 Carbon Fixation --> X3
2)very unstable molecule immediately splits to form 2 molecules of 3 PGA (carbonphosphoglycerate)
P-C-C-C C-C-C-P

9. We are in the STROMA

10. forming 1, 3 biphosphoglycerate
phase 2 Carbon - Reduction > X3
addt’l phosphate group to each 3-phosphoglycerate from ATP (from light reaction) :
P-C-C-C-P P-C-C-C-P
forming 1, 3 biphosphoglycerate

11. We are in the STROMA

12. (stores more potential energy) (same sugar as in glycolysis)
phase 2 C - Reduction --> (X3)
2)reduced (e- gained) by NADPH (from light reaction) to make G3P
P-C-C-C P-C-C-C
(stores more potential energy)
(same sugar as in glycolysis)

13. We are in the STROMA

14. phase 2 Reduction --> (X3)
3)one G3P molecule exits (used later by the plant)
P-C-C-C P-C-C-C
P-C-C-C
P-C-C-C

15. We are in the STROMA

16. phase 3 Regeneration of CO2 acceptor RuBP -->
1) series of reactions rearranges the 5 G3P molecules into 3 RuBP …
using up 3 more ATP’s.

17. We are in the STROMA

18. RuBP is then
prepared to receive
CO2 again

19. For 1 G3P molecule the one that exited… (precursor to sugar) the cycle:
uses 9 ATP
uses 6 NADPH
uses 3 CO2

20. We are in the STROMA
(6)