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P680

Stroma. Step 1: Resonance Energy Transfer (“Photonic Pinball”) with photon ultimately absorbed by P680. (Photon). Primary Electron acceptor. P680. Light-harvesting Complexes. Pigment molecule. PHOTOSYSTEM II (PS II). Thylakoid Space. Stroma. Step 1:

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P680

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  1. Stroma Step 1: Resonance Energy Transfer (“Photonic Pinball”) with photon ultimately absorbed by P680 (Photon) Primary Electron acceptor P680 Light-harvesting Complexes Pigment molecule PHOTOSYSTEM II (PS II) Thylakoid Space

  2. Stroma Step 1: Resonance Energy Transfer (“Photonic Pinball”) with photon ultimately absorbed by P680 Primary Electron acceptor P680 Light-harvesting Complexes Pigment molecule PHOTOSYSTEM II (PS II) Thylakoid Space

  3. Stroma Step 2: Excited electron stripped from P680 & passed to primary electron acceptor (pheophytin) Primary Electron acceptor e- P680 Reaction Center Pigment molecule PHOTOSYSTEM II (PS II) Thylakoid Space

  4. Stroma Step 3: Electrons are passed from primary electron acceptor to plastoquinone (Pq) Plastoquinone Primary Electron acceptor e- P680+ Pigment molecule PHOTOSYSTEM II (PS II) Thylakoid Space

  5. Stroma Step 3: Electrons are passed from primary electron acceptor to plastoquinone (Pq) Plastoquinone Primary Electron acceptor e- P680+ Pigment molecule PHOTOSYSTEM II (PS II) Thylakoid Space

  6. Step 4: Photolysis – an enzyme catalyzes the splitting of water into 2e-, 2H+, and oxygen; electrons are delivered to P680+ to replace those lost & O2 is given off as byproduct Stroma Plastoquinone Primary Electron acceptor e- P680 Pigment molecule H2O  2e- + ½ O2 + 2H+ Thylakoid Space

  7. 2H+ Plastoquinone Step 5: Electrons are passed from plastoquinone (Pq) to Cytochrome Complex e- Cytochrome complex Plastocyanin

  8. 2H+ Step 6: Transport of electrons leads to pumping of H+ across thylakoid membrane, creating a concentration gradient Plastoquinone e- Cytochrome complex Plastocyanin

  9. Step 7: Electrons are passed from Cytochrome Complex to Plastocyanin (Pc) Plastoquinone Cytochrome complex Plastocyanin e- 2H+

  10. Stroma Step 8: Resonance Energy Transfer (“Photonic Pinball”) with photon ultimately absorbed by P700 Primary Electron acceptor P700 Light-harvesting Complexes Pigment molecule PHOTOSYSTEM I (PS I) Thylakoid Space

  11. Stroma Step 8: Resonance Energy Transfer (“Photonic Pinball”) with photon ultimately absorbed by P700 Primary Electron acceptor P700 Reaction Center Pigment molecule PHOTOSYSTEM I (PS I) Thylakoid Space

  12. Stroma Step 9: P700 has excited electron stripped by primary electron acceptor (phylloquinone); Pc delivers e- to P700+ to replace those just lost/stripped Primary Electron acceptor Plastocyanin e- e- P700 Reaction Center Pigment molecule PHOTOSYSTEM I (PS I) Thylakoid Space

  13. Stroma Step 9: P700 has excited electron stripped by primary electron acceptor (phylloquinone); Pc delivers e- to P700+ to replace those just lost/stripped Primary Electron acceptor e- + Plastocyanin P700 e- Pigment molecule PHOTOSYSTEM I (PS I) Thylakoid Space

  14. Step 10: Primary electron acceptor passes e- to Ferredoxin (Fd) Stroma Primary Electron acceptor Ferredoxin e- e- Plastocyanin P700 Pigment molecule Thylakoid Space

  15. Step 10: Primary electron acceptor passes e- to Ferredoxin (Fd) Stroma Primary Electron acceptor Ferredoxin e- e- P700 Pigment molecule PHOTOSYSTEM I (PS I) Thylakoid Space

  16. Step 10: Primary electron acceptor passes e- to Ferredoxin (Fd) Stroma Primary Electron acceptor e- Ferredoxin e- P700 Pigment molecule PHOTOSYSTEM I (PS I) Thylakoid Space

  17. Step 11: Fd passes electrons to NADP+reductase which catalyzes the reduction of NADP+ to NADPH Stroma e- Ferredoxin NADP+ Reductase Thylakoid Space

  18. Step 11: Fd passes electrons to NADP+reductase which catalyzes the reduction of NADP+ to NADPH Stroma e- Ferredoxin NADP+ Reductase Thylakoid Space

  19. Step 11: Fd passes electrons to NADP+reductase which catalyzes the reduction of NADP+ to NADPH Stroma NADP+ Ferredoxin NADP+ Reductase 2e- NADPH Thylakoid Space

  20. Step 12: ATP Synthase uses the H+ (chemiosmotic) gradient to synthesize ATP as H+ diffuse from thylakoid space to the stroma Stroma ATP ADP + Pi ATP Synth-ase 4 H+ Thylakoid Space

  21. H2O CO2 Light NADP+ ADP CALVIN CYCLE LIGHT REACTIONS ATP NADPH O2 [CH2O] (sugar) STROMA (Low H+ concentration) LE 10-17 Cytochrome complex Photosystem I Photosystem II Light NADP+ reductase Light 2 H+ NADP+ + 2H+ Fd NADPH + H+ Pq Pc H2O O2 1/2 THYLAKOID SPACE (High H+ concentration) 2 H+ +2 H+ To Calvin cycle Thylakoid membrane ATP synthase STROMA (Low H+ concentration) ADP + ATP P i H+

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