1. Overview of Photosynthesis
importance: fix tons of CO2 per year, used as energy for virtually all organisms
similarity to ETC/ox-phos, PPP and tied to gng
2 phases
light-dependent rxns (light rxns)
light-independent rxns (dark rxns)
location: chloroplast

2. Detailed Chloroplast Structure
Porous outer membrane, tight inner membrane
Stroma
thylakoid disk
granum (grana)
thylakoid lumen
Light rxns take place on thylakoid membrane, dark rxns stroma

3. Light is Captured by Several Classes of Molecules Fig
Light is Captured by Several Classes of Molecules Fig (a) Lehninger POB 4th Ed.
Chlorophylls

4. Light is Captured by Several Classes of Molecules Fig
Light is Captured by Several Classes of Molecules Fig (b)-(d) Lehninger POB 4th Ed.
Carotenoids and other conjugated compounds

5. Light Reactions Fig. 19-41 Lehninger POB 4th Ed.
Reason for numerous molecules

6. Light Reactions Fig. 19-45 Lehninger POB 4th Ed.
“Special Pair”
Photosystems I and II

7. Photosystem I (P700) Fig. 19-49 Lehninger POB 4th Ed.
Not confident all molecules have been ID’d
Major molecules
Some of the reactions which occur
NADPH produced

8. Photosystem II (P680) Fig. 19-49 Lehninger POB 4th Ed.
Major molecules
ATP produced

9. PSI and PSII Together Form the “Z-scheme”

10. Photophosphorylation Fig. 19-54(c) Lehninger POB 4th Ed.
Proton gradient develops as e– are transported
high pH inside thylakoid lumen

11. Water Splitting Complex Science 292:447, 2001
PSII does not directly perform sequential one-e– transfers
Rather, it has an integral inorganic catalyst from which it extracts 4 e– and then reacts with 2 H2Os to form O2
4 Mn electronically coupled as Mn4 cluster

12. Photophosphorylation
Proton gradient develops as e– are transported
high pH inside thylakoid lumen
protons come out through Fo of “C-ATPase” (CFo)
F1 rotor forms ATP (CF1)

13. Cyclic Photophosphorylation Fig. 19-49 Lehninger POB 4th Ed.
P700 only
NO NADPH produced, only ATP (less)
Major molecules: P700, Fd, Cyt. B6, Cyt f, PC

14. ~Idealized Balanced Net Rxn

15. Dark Reactions - C3 plants
3PG first molecule produced containing the fixed carbon

16. Dark Reactions - C3 plants
3PG first molecule produced containing the fixed carbon

17. Dark Reactions - C3 plants
3PG first molecule produced containing the fixed carbon

18. Dark Reactions – Rubisco Reaction
rubisco is the most abundant protein in the world

19. 3PG  Glucose
What rxns are required?

20. Regeneration of Ribulose-1,5-bisphosphate

21. ~Idealized Balanced Net Rxn

22. C4 Plants The Hatch-Slack Pathway Fig. 20-23 Lehninger POB 4th Ed.
Molecular logic
Division of labor
Additional Reactions

23. Additional Rxns of the Hatch-Slack Pathway Fig
Additional Rxns of the Hatch-Slack Pathway Fig Lehninger POB 4th Ed.

24. Regulation Occurs Several Ways Fig. 20-18 Lehninger POB 4th Ed.
Regulation by light
a. FBPase activated
b. light-induced Mg2+ efflux to stroma
c. thioredoxin
2. Rubisco Allosterism
(a) carbamoylation stim
(b) rib-1,5-P2 inh. Carb.
(c) B overcome ATP?
(d) 2-carboxyarabinitol-1-phosphate