Chapter 10 Plant metabolism - photosynthesis

1. Chapter 10Plant metabolism - photosynthesis

2. Photosynthesis • Photosynthesis is an anabolic process that combines carbon dioxide and water in the presence of light with the aid of chlorophyll and transforms the energy from the sun to biochemical energy in the bonds between the atoms in a sugar molecule; oxygen is a by-product.

3. Photosynthesis • Photosynthesis is an anabolic process that combines carbon dioxide and water in the presence of light with the aid of chlorophyll and transforms the energy from the sun to biochemical energy in the bonds between the atoms in a sugar molecule; oxygen is a by-product. C-source Global warming

4. Photosynthesis • Photosynthesis is an anabolic process that combines carbon dioxide and water in the presence of light with the aid of chlorophyll and transforms the energy from the sun to biochemical energy in the bonds between the atoms in a sugar molecule; oxygen is a by-product. Isotope Sole source of O2

5. Photosynthesis • Photosynthesis is an anabolic process that combines carbon dioxide and water in the presence of light with the aid of chlorophyll and transforms the energy from the sun to biochemical energy in the bonds between the atoms in a sugar molecule; oxygen is a by-product. P680 P700

6. Photosynthesis • Photosynthesis is an anabolic process that combines carbon dioxide and water in the presence of light with the aid of chlorophyll and transforms the energy from the sun to biochemical energy in the bonds between the atoms in a sugar molecule; oxygen is a by-product.

7. Photosynthesis • … transforms the energy from the sun to biochemical energy in the bonds between the atoms in a sugar molecule; oxygen is a by-product. O2 Electron flow (Z scheme) ATP NADPH Calvin cycle RuBP CO2 ADP NADP Light-independent reaction Carbon-fixing and reducing reaction H2O Light-dependent reaction

8. Photosynthesis • Water molecules are split, releasing e-, H+, and O2 • e- passing along electron transport system • H+ is involved in NADP to form NADPH • ATP molecules are produced O2 ATP NADPH Z scheme ADP NADP H2O Light-dependent reaction

9. Photosynthesis Light-dependent reaction • Water molecules are split, releasing e-, H+, and O2

10. Photosynthesis Light-dependent reaction • Water molecules are split, releasing e-, H+, and O2 • Electron flow: e- passing along electron transport system Z scheme

11. Photosynthesis Light-dependent reaction • Water molecules are split, releasing e-, H+, and O2 • e- passing along electron transport system • H+ is involved in NADP to form NADPH

12. Photosynthesis Light-dependent reaction • Water molecules are split, releasing e-, H+, and O2 • e- passing along electron transport system • H+ is involved in NADP to form NADPH • ATP molecules are produced Photophosphorylation

13. Photosynthesis • … transforms the energy from the sun to biochemical energy in the bonds between the atoms in a sugar molecule; oxygen is a by-product. O2 Electron flow (Z scheme) ATP NADPH Calvin cycle RuBP CO2 ADP NADP Light-independent reaction Carbon-fixing and reducing reaction H2O Light-dependent reaction

14. Photosynthesis Light-independent reaction • Water Calvin cycle

15. Photosynthesis Light-independent reaction • Carboxylation 6 CO2 + 6RuBP Rubisco (RuBPcarboylase/oxygenase) 12 3PGA Calvin cycle

16. Photosynthesis Light-independent reaction • Carboxylation • Reduction 6 CO2 + 6RuBP Rubisco (RuBPcarboylase/oxygenase) Calvin cycle 12 3PGA 12 GA3P

17. Photosynthesis Light-independent reaction • Carboxylation • Reduction • Regeneration 6 CO2 + 6RuBP Rubisco (RuBPcarboylase/oxygenase) Calvin cycle 12 3PGA + 10 GA3P 2 GA3P 6RuBP

18. Photosynthesis

19. Photosynthesis vs. photorepiration • Stomata are closed under hot and dry climates, which leads to a decreased CO2:O2 ratio and hence promote photorespiration

20. Photosynthesis vs. photorepiration • How to inhibit photorespiration and hence promote fixation of CO2 O2 Electron flow (Z scheme) ATP NADPH Photo-respiration Calvin cycle RuBP CO2 ADP NADP H2O

21. Photosynthesis vs. photorepiration • How to inhibit photorespiration and hence promote fixation of CO2 Photo-respiration Calvin cycle RuBP CO2 Increasing CO2:O2 ratio

22. Photosynthesis: the 4-Carbon pathway • CO2 are combined with PEP (a 3-carbon compound), producing OAA (a 4-carbon compound) in mesophyll cells • The 4-carbon compounds are transported to the bundle sheath cellswhere CO2 are released, concentrated and enter the Calvin cycle.

23. Photosynthesis: the 4-Carbon pathway • Mesophyll cells: CO2 + PEP → OAA • Bundle sheath cells:4-C → CO2 → Calvin cycle. Kranz anatomy leave

24. Photosynthesis vs. photorepiration • How to inhibit – C4 photosynthesis Mesophyll cell - OAA BSC – concentrated CO2 O2 Electron flow (Z scheme) ATP NADPH Photo-respiration Calvin cycle RuBP CO2 ADP NADP H2O

25. Photosynthesis: CAM pathway • Night: CO2+ PEP → OAA → malic acid accumulating organic acids in vacuole • Day: 4-C → CO2 → Calvin cycle releasing CO2 in mesophyll cell

26. Photosynthesis Mesophyll cell - OAA BSC – concentrated CO2 C3plant C4 plant CAMplant O2 Electron flow (Z scheme) ATP NADPH Photo-respiration Calvin cycle RuBP CO2 ADP NADP H2O Day – concentrated CO2 in mesophyll cell Night – accumulating organic acids in vacuole