1. Next Assignment? In lab time Friday March 27 or in class starting March 27 or March 30? GMO plants? Herbicide resistance Pathogen/herbivore resistance Improving nutrition Making vaccines, other useful biochems Plant/Algal biofuels?

2. PSI and PSII work together in the “Z-scheme” Light absorbed by PS II makes ATP Light absorbed by PS I makes reducing power

3. cyclic non-cyclic Ultimate e - sourceNonewater O 2 released?Noyes Terminal e - acceptorNoneNADP+ Form in which energy isATPATP & temporarily capturedNADPH Photosystems requiredPSIPSI & PSII

4. Z-scheme energetics

5. PSII Photochemistry 1) LHCII absorbs a photon 2) energy is transferred to P680

6. PSII Photochemistry 3) P680* reduces pheophytin ( chl a with 2 H + instead of Mg 2+ ) = primary electron acceptor

7. PSII Photochemistry 3) P680* reduces pheophytin ( chl a with 2 H + instead of Mg 2+ ) = primary electron acceptor charge separation traps the electron

8. PSII Photochemistry 4) pheophytin reduces PQA (plastoquinone bound to D2) moves electron away from P680 + & closer to stroma

9. PSII Photochemistry 5) PQA reduces PQB (forms PQB - )

10. PSII Photochemistry 6) P680 + acquires another electron, and steps 1-4 are repeated

11. PSII Photochemistry 7) PQA reduces PQB - -> forms PQB 2-

12. PSII Photochemistry 8) PQB 2- acquires 2 H + from stroma forms PQH 2 (and adds to ∆pH)

13. PSII Photochemistry 9) PQH2 diffuses within bilayer to cyt b6/f - is replaced within D1 by an oxidized PQ

14. Photolysis: Making Oxygen 1) P680 + oxidizes tyrZ ( an amino acid of protein D1)

15. Photolysis: Making Oxygen 2) tyrZ + oxidizes one of the Mn atoms in the OEC Mn cluster is an e - reservoir

16. Photolysis: Making Oxygen 2) tyrZ + oxidizes one of the Mn atoms in the OEC Mn cluster is an e - reservoir Once 4 Mn are oxidized replace e - by stealing them from 2 H 2 O

17. Shown experimentally that need 4 flashes/O2

18. Mn cluster cycles S 0 -> S 4 Reset to S 0 by taking 4 e - from 2 H 2 O

19. Electron transport from PSII to PSI 1) PQH 2 diffuses to cyt b 6 /f 2) PQH2 reduces cyt b 6 and Fe/S, releases H + in lumen since H + came from stroma, transports 2 H + across membrane (Q cycle)

20. Electron transport from PSII to PSI 3) Fe/S reduces plastocyanin via cyt f cyt b 6 reduces PQ to form PQ -

21. Electron transport from PSII to PSI 4) repeat process, Fe/S reduces plastocyanin via cyt f cyt b 6 reduces PQ - to form PQH2

22. Electron transport from PSII to PSI 4) PC (Cu + ) diffuses to PSI, where it reduces an oxidized P700

23. Electron transport from PSI to Ferredoxin 1) LHCI absorbs a photon 2) P700* reduces A0 3) e- transport to ferredoxin via A1 & 3 Fe/S proteins

24. Electron transport from Ferredoxin to NADP+ 2 Ferredoxin reduce NADP reductase

25. Electron transport from Ferredoxin to NADP+ 2 Ferredoxin reduce NADP reductase reduces NADP+

26. Electron transport from Ferredoxin to NADP+ 2 Ferredoxin reduce NADP reductase reduces NADP+ this also contributes to ∆pH

27. Overall reaction for the Z-scheme 8 photons + 2 H 2 O + 10 H + stroma + 2 NADP + = 12 H + lumen + 2 NADPH + O 2

28. Chemiosmotic ATP synthesis PMF mainly due to ∆pH is used to make ATP

29. Chemiosmotic ATP synthesis PMF mainly due to ∆pH is used to make ATP -> very little membrane potential, due to transport of other ions

30. Chemiosmotic ATP synthesis PMF mainly due to ∆pH is used to make ATP -> very little membrane potential, due to transport of other ions thylakoid lumen pH is < 5 cf stroma pH is 8

31. Chemiosmotic ATP synthesis PMF mainly due to ∆pH is used to make ATP -> very little membrane potential, due to transport of other ions thylakoid lumen pH is < 5 cf stroma pH is 8  pH is made by ETS, cyclic photophosphorylation,water splitting & NADPH synth

32. Chemiosmotic ATP synthesis Structure of ATP synthase CF1 head: exposed to stroma CF 0 base: Integral membrane protein

33. a & b 2 subunits form stator that immobilizes  &  F1 subunits a is also an H + channel c subunits rotate as H + pass through  &  also rotate c,  &  form a rotor

34. Binding Change mechanism of ATP synthesis H+ translocation through ATP synthase alters affinity of active site for ATP

35. Binding Change mechanism of ATP synthesis H+ translocation through ATP synthase alters affinity of active site for ATP ADP + Pi bind to  subunit then spontaneously form ATP

36. Binding Change mechanism of ATP synthesis H+ translocation through ATP synthase alters affinity of active site for ATP ADP + Pi bind to  subunit then spontaneously form ATP ∆G for ADP + Pi = ATP is ~0 role of H+ translocation is to force enzyme to release ATP!

37. Binding Change mechanism of ATP synthesis 1) H + translocation alters affinity of active site for ATP 2) Each active site ratchets through 3 conformations that have different affinities for ATP, ADP & Pi due to interaction with the  subunit

38. Binding Change mechanism of ATP synthesis 1) H + translocation alters affinity of active site for ATP 2) Each active site ratchets through 3 conformations that have different affinities for ATP, ADP & Pi 3) ATP is synthesized by rotational catalysis g subunit rotates as H + pass through Fo, forces each active site to sequentially adopt the 3 conformations

39. Evidence supporting chemiosmosis 1) ionophores (uncouplers) 2) can synthesize ATP if create ∆pH a) Jagendorf expt: soak cp in pH 4 in dark, make ATP when transfer to pH 8