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The Dark SideThe Dark Side of of PhotosynthesisPhotosynthesis
In stromaIn stroma
In 3 In 3
stagesstages
Dark Reaction/ Dark Reaction/ Calvin CycleCalvin Cycle
of of PhotosynthesisPhotosynthesis In stromaIn stroma
In 3 In 3
stagesstages
Dark Reaction/Dark Reaction/ Calvin Calvin
CycleCycle
uses ATP ATP and NADPHNADPH (from light
reaction) to convert COCO22 to sugarsugar
Dark Reaction/Dark Reaction/ Calvin Calvin
CycleCyclePhase 1: Phase 1: Carbon Carbon FixationFixationPhase 2: Phase 2: ReductionReductionPhase 3:Phase 3: Regeneration Regeneration of RuBPof RuBP
We are in the We are in the STROMASTROMA
We are in the We are in the STROMASTROMA
phase 1 Carbon Carbon FixationFixation --> X3
1)CO2 attaches to a 5C sugar Ribulose Biphosphate (RuBP) via. via. RubiscoRubisco:
P-C-C-C-C-C-C-P
Rubisco (RuBP carboxylase) = Rubisco (RuBP carboxylase) = enzymeenzyme
phase 1 Carbon Fixation --> X3
2)very unstable molecule. .. immediately splits to form 2 molecules of 3 PGA3 PGA
(carbonphosphoglycerate)
P-C-C-C C-C-C-P
We are in the We are in the STROMASTROMA
phase 2 Carbon - Reduction
--> X3
1) 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
We are in the We are in the STROMASTROMA
phase 2 C - Reduction --> (X3)
2)reduced (e- gained) by NADPH (from light reaction) to make G3PG3P
P-C-C-C P-C-C-C
P-C-C-C P-C-C-C
P-C-C-C P-C-C-C•(stores more potential energy)•(same sugar as in glycolysis)
We are in the We are in the STROMASTROMA
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
P-C-C-C
P-C-C-C
We are in the We are in the STROMASTROMA
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.
We are in the We are in the STROMASTROMA
For 1 G3P molecule the one that
exited… (precursor to sugar) the cycle:•uses 9 ATP
•uses 6 NADPH
•uses 3 CO2
We are in the We are in the STROMASTROMA
(6)