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Monday’s Topics Overview of photosynthesis Key early photosynthesis experiments

Monday’s Topics Overview of photosynthesis Key early photosynthesis experiments Photosynthesis: light reactions. From which molecule does the O2 released by plants come from? What happens to H20 during photosynthesis? (more than one answer might be correct) a. Oxidized

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Monday’s Topics Overview of photosynthesis Key early photosynthesis experiments

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  1. Monday’s Topics • Overview of photosynthesis • Key early photosynthesis experiments • Photosynthesis: light reactions

  2. From which molecule does the O2 released by plants come from? What happens to H20 during photosynthesis? (more than one answer might be correct) a. Oxidized b. Reduced c. Activated d. Looses electrons e. Gains electrons Which are the energy rich compounds generated during the light reactions?

  3. Today’s Topics • Electron transfer during the light reactions • Regulation of photosynthesis • Evolution of photosynthetic systems

  4. The Electron Transfer Process Energy H20 2 H+ + ½ O2

  5. Duysens & Amesz (1962) PSI + PSII Light Darkness Oxidized State PSI Light Cytochrome PSI Light Reduced State Time

  6. Z-Scheme: Electron transfers (redox reactions)

  7. Photosynthesis: Light Reactions

  8. Reactions of Plastoquinones

  9. Photosynthesis: Light Reactions

  10. Electron Transfer in the Cytochrome b6f Complex

  11. Electron Transfer in the Cytochrome b6f Complex

  12. Photosynthesis: Light Reactions

  13. Herbicides and the study of photosynthesis Blocks electron transfer in PSI Blocks electron transfer to plastoquinone

  14. Excercises What will the status of the plastoquinone pool in DCMU treated plants? a. Reduced b. Oxidiced What will the status of the plastocyanin pool be in Paraquot treated plants? a. Reduced b. Oxidiced

  15. Photosynthesis: Light Reactions

  16. Today’s Topics • Electron transfer during the light reactions • Regulation of photosynthesis • Evolution of photosynthetic systems

  17. Problems with the electron transfer process • Excess energy absorbance • Electron balances between PSI and PSII

  18. Problems with the electron transfer process Energy H20 2 H+ + ½ O2

  19. PHOTOPROTECTION

  20. Nonphotochemical Quenching • Reorganization of antenna complexes • Special carotenoids: xantophylls • Thylakoid lumen pH

  21. Problems with the electron transfer process • Excess energy absorbance • Electron balances between PSI and PSII

  22. Energy partitioning between photosystems LHCII LHCII-P

  23. Topics • Electron transfer during the light reactions • Regulation of photosynthesis • Evolution of photosynthetic systems

  24. How does a plant make more chloroplasts? Where are chloroplast proteins made? Where do the chloroplasts come from? Do all chloroplasts in all algae and plants have the same origin?

  25. What are the main open questions about the origin of oxygenic photosynthesis? Which are the current hypothesis to explain the beginning of oxygenic photosynthesis?

  26. Next lecture: -Carbon reactions of photosynthesis Light Reactions Carbon Reactions ATP NADPH H20 O2 CO2 CH20

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