monday’s topics overview of photosynthesis key early photosynthesis experiments
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Monday’s Topics Overview of photosynthesis Key early photosynthesis experiments Photosynthesis: light reactions. From which molecule does the O2 released by plants come from? What happens to H20 during photosynthesis? (more than one answer might be correct) a. Oxidized - PowerPoint PPT PresentationTRANSCRIPT
Monday’s Topics
1.Overview of photosynthesis2.Key early photosynthesis experiments3. Photosynthesis: light reactions
From which molecule does the O2 released by plants come from?
What happens to H20 during photosynthesis? (more than one answer might be correct)
a. Oxidizedb. Reducedc. Activatedd. Looses electronse. Gains electrons
Which are the energy rich compounds generated during the light reactions?
Today’s Topics
1.Electron transfer during the light reactions2.Regulation of photosynthesis3.Evolution of photosynthetic systems
Ener
gy
H20
2 H+ + ½ O2
The Electron Transfer Process
Oxidized State
Reduced State
PSI Light
PSI + PSII Light
PSI Light
Darkness
Time
Duysens & Amesz (1962)
Cytochrome
Z-Scheme: Electron transfers (redox reactions)
Photosynthesis: Light Reactions
Reactions of Plastoquinones
Photosynthesis: Light Reactions
Electron Transfer in the Cytochrome b6f Complex
Electron Transfer in the Cytochrome b6f Complex
Photosynthesis: Light Reactions
Herbicides and the study of photosynthesis
Blocks electron transfer to plastoquinone
Blocks electron transfer in PSI
Excercises
What will the status of the plastoquinone pool in DCMU treated plants?a. Reducedb. Oxidiced
What will the status of the plastocyanin pool be in Paraquot treated plants?a. Reducedb. Oxidiced
Photosynthesis: Light Reactions
Today’s Topics
1.Electron transfer during the light reactions2.Regulation of photosynthesis3.Evolution of photosynthetic systems
Problems with the electron transfer process
A. Excess energy absorbanceB. Electron balances between PSI and PSII
Ener
gy
H20
2 H+ + ½ O2
Problems with the electron transfer process
PHOTOPROTECTION
Nonphotochemical Quenching
a. Reorganization of antenna complexes
b. Special carotenoids: xantophylls
c. Thylakoid lumen pH
Problems with the electron transfer process
A. Excess energy absorbanceB. Electron balances between PSI and PSII
Energy partitioning between photosystems
LHCII LHCII-P
Topics
1.Electron transfer during the light reactions2.Regulation of photosynthesis3.Evolution of photosynthetic systems
How does a plant make more chloroplasts?
Where do the chloroplasts come from?
Do all chloroplasts in all algae and plants have the same origin?
Where are chloroplast proteins made?
What are the main open questions about the origin of oxygenic photosynthesis?
Which are the current hypothesis to explain the beginning of oxygenic photosynthesis?
Next lecture:-Carbon reactions of photosynthesis
Light ReactionsLight ReactionsATP
NADPHCarbon
ReactionsCarbon
Reactions
H20 O2 CO2 CH20