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

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