1. Topics: 1.CO2 concentrating mechanisms 2.Starch and Sucrose synthesis

2. RuBis Carboxylase/Oxygenase

3. The cost of photorespiration 3x O 2 needs 2x ATP and 2x Ferredoxin AND high temperature increases photorespiration: *Modifies Rubisco’s kinetics: oxygenation more favorable *Decreases the CO 2 /O 2 ratio in solution Why do they do this?

4. What do plants do?

5. CO 2 Concentrating Mechanisms a)CO 2 and HCO 3 - Pumps b)C 4 Photosynthesis c)Crassulacean Acid Metabolism (CAM)

6. (Tanaka et al., 2008; Yeates Lab, UCLA) Nevo et al., 2007 Carboxysomes: Rubisco, Carbonic anhydrase CO 2 and HCO 3 - Pumps: Aquatic Organisms Cyanobacteria Thylakoid

7. CO 2 Concentrating Mechanisms a)CO 2 and HCO 3 - Pumps b)C 4 Photosynthesis c)Crassulacean Acid Metabolism (CAM) PEP-Carboxylase CH 2 II C-OPO 3 2- + HCO 3 - I COO - I CH 2 + HPO 4 2- I C=O I COO -

8. Could plants just use PEP-carboxylase instead of Rubisco?

9. C3 + HCO 3 - C4 C3 + CO 2 HCO 3 - CO 2 RUBISCO C3 Fixation/carboxylation C4 transport Decarboxylation C3-”recycling”

10. The C4 carbon cycle: Spatial separation a.Different Cells: Bundle Sheath cells/ Kranz anatomy b.Within one cell

11. Kranz Anatomy Bundle sheath cells

12. The C4 carbon cycle: Spatial separation Unstacked thylakoids (PSI) Starch Stacked thylakoids (PSI+PSII) No starch CHLOROPLASTS

13. The C4 carbon cycle: Modifications Convergent evolution

14. (V Single Cell C4 Photosynthesis Borszczowia Bienertia Voznesenskaya et al., 2002

15. CO 2 Concentrating Mechanisms a)CO 2 and HCO 3 - Pumps b)C 4 Photosynthesis c)Crassulacean Acid Metabolism (CAM) PEP-Carboxylase CH 2 II C-OPO 3 2- + HCO 3 - I COO - I CH 2 + HPO 4 2- I C=O I COO -

16. CAM: temporal separation Minimizing water loss H20 loss/CO2 gained (g) CAM 50-100g C4250-300g C3 400-500

17. CAM: Day/Night switch

18. CO 2 Concentrating Mechanisms a)CO 2 and HCO 3 - Pumps b)C 4 Photosynthesis c)Crassulacean Acid Metabolism (CAM) PEP-Carboxylase CH 2 II C-OPO 3 2- + HCO 3 - I COO - I CH 2 + HPO 4 2- I C=O I COO -

19. PEPC regulation C4 PEPC P P PEPC- Kinase ATPADP P P PEPC- Kinase PEPC P P PEPC- Kinase ATPADP P P Metabolites Salt stress Circadian clock CAM

20. Topics: 1.CO2 concentrating mechanisms 2.Starch and Sucrose synthesis

22. Triose-P Glc-1-P Glc-NtDP NTP (ATP/UTP) PPi S a c c h a ri d e s Saccharide Synthesis: Overview Pi

23. Plastids: Starch Synthesis

24. Remember: Cellulose =  -D-1,4-glucosyl Starch is a branched polymer

26. PHOSPHOROLYTICHYDROLYTIC

27. Triose-P Glc-1-P Glc-NtDP NTP (ATP/UTP) PPi S a c c h a ri d e s Saccharide Synthesis: Overview Pi

28. Triose-P Fru-1,6-bisP Fru-6-P Glc-6-P Glc-1-P UDP-Glc Suc-6-P Pi PPi ATP ADP PPi UTP Pi Sucrose SPS

29. Regulation of Starch and Sucrose Synthesis Pi Fru-1,6-bisP Fru-6-PFru-2,6-bisP Fru-1,6-bisP-Phosphatase UDP-Glc + Fru-6-PSuc-6P Sucrose-P Synthase (SPS) Glc-6-P SPS-P SPS Pi Glc-1-P ADP-Glc ATP PPi 2xPi Pi 3PGA Ferredoxin Red. ADP-Glc Pyrophosphorylase (AGPase)

30. Cytosol Plastid Triose-P Pi Sucrose Synthesis Starch Synthesis Balance: Starch vs Sucrose Synthesis