1. The Light Reactions of Photosynthesis
A Fast Run Through Plants
Chapter 19:
The Light Reactions of Photosynthesis

2. Each Year
1010 tons of carbon fixed
1017 kcal free energy

3. The Light Reactions

5. Chlorophyll
=100,000 M-1 cm-1

6. Two Chloroplast Photosystems
Overview animation of Photosynthesis

8. PS II
Read this Tutorial of PSII

9. PS II
See Animation of PSII

10. Oxidizing Water! Each photon “pulls off” an electron

11. PS II- generates H+ gradient too (Jagendorf,1966)

12. Cyt bf complex: a lot like cyt.c-Q oxidoreductase

13. PS I
Read this Tutorial of PSI

14. PS I

15. Know the “Z” Scheme !
Overview animation of Photosynthesis

16. Overall Photosynthesis gives:
ENERGETICS
In chloroplasts pH= 3.5
So, G= kcal /mol H+ and there are ~4 H+/ ATP
DG = 2.3 RT (pHthylakoid - pHstroma)
+ FDY(out relative to in)
Overall Photosynthesis gives:
8 photons = 1O2, 2 NADPH, 3 ATP
( a 700 nm photon has kcal /mole potentially)

17. Cyclic Photophosphorylation: for ATP, only when NADPH is high!