fig 7.22 in the light, acidification of the lumen creates a ph gradient across thylakoid membranes
TRANSCRIPT
Fig 7.22
In the light, acidification of the lumen creates a pH gradient across thylakoid membranes.
ATP-synthase is a protein motor
Driving force is chemiosmotic
gradient(Mitchell 1960s)
Fig 7.33
Jagendorf experiment:
Acidified lumen drives ATP synthesis in dark
Fig 7.32
I. Overview
How do herbicides that are inhibitors of electron transport activity work?
Some herbicides are inhibitors of electron transport
Blocks electron flow Intercepts electrons
Fig 7.31
Some herbicides are inhibitors of electron transport
Fig 7.31
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-2
0
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0 500 1000 1500 2000
PAR, µmol photons m -2 s-1
Net CO
2 uptake, µmol m
-2 s
-1
Light response of photosynthesis in redwood, Sequoia sempervirens.
Summary of photophosphorylation
Fig 7.34
The use of a proton gradient to produce ATP is common theme in biology.
Purple bacteria have only PSI and ATPsynthase
But they do have ATP-ase
Fig 7.34
Mitochondria also have electron transport chain and ATP synthase
Oxidative phosphorylation
Fig 7.34
Products and substrates of Light and Dark reactions
Substrate Energy source
Products Location
Light reactions
H2O light NADPH
ATP
Thylakoids
Dark reactions
CO2 NADPH ATP
Sugars Stroma
Summary of the Light Reactions
The Carbon Reaction of photosynthesisUsing ATP and NADPH to produce carbohydratesfrom CO2.
Products and substrates of Light and Dark reactions
Substrate Energy source
Products Location
Light reactions
H2O light NADPH
ATP
Thylakoids
Dark reactions
CO2 NADPH ATP
Carbo-hydrates
Stroma
The “dark” or Carbon Reduction Reactions
Products and substrates of Light and Dark reactions
Substrate Energy source
Products Location
Light reactions
H2O light NADPH
ATP
Thylakoids
Dark reactions
CO2 NADPH ATP
Carbo-hydrates
Stroma
Relating the Light and Dark Reactions
Photosynthesis: Carbon Reactions (Chapter 8)
Photosynthetic CO2 uptake uses the products of thelight reactions to enable the “dark” or carbon reductionreactions.
-4
-2
0
2
4
6
8
10
12
14
0 500 1000 1500 2000
PAR, µmol photons m -2 s-1
Net CO
2 uptake, µmol m
-2 s
-1
Light response of photosynthesis in redwood, Sequoia sempervirens.
Conceptual linkage between the light and carbon
reactions of photosynthesis.
Fig. 8.1
I. Basics of the carbon reactionsthe Calvin cycle and C3 photosynthesis
II. Photorespiration - a process of O2 reduction thatcompetes with CO2 reduction and reduces the rateof carbon fixation.
III. CO2 concentrating mechanisms - variation on the “C3” photosynthetic metabolism.
C4 photosynthesis - an adaptation to warm and dry environments
CAM metabolism - an adaptation that greatly increaseswater use efficiency.
Fig. 8.2
The Calvin Cycle(reductivepentose phosphatecycle)
3 Stages•Carboxylation•Reduction•Regeneration
A 3 carbon molecule
An outline of C3 photosynthesis
Carboxylation•The key initial step in C3 photosynthesis•RUBP + CO2 ---> 3-PGA •Catalyzed by “Rubisco”: ribulose 1,5-bisphosphate carboxylase-oxygenase• binds the 5C RUBP molecule and 1C CO2, making two 3C molecules.
5 C + 1 C -----> 2 x 3C molecules
Fig. 8.3 (partial)
Fig. 8.2
•Carboxylation•Reduction•Regeneration
Reduction steps of the Calvin Cycle use ATP and NADPH to produce a carbohydrate, glyceraldehyde 3 phosphate.
3PGA + ATP + NADPH --> G3P
G3P can be used to make sucrose or starch
Reduction
Fig. 8.3 (partial) - the reduction steps
Fig. 8.2
•Carboxylation•Reduction•Regeneration
RegenerationThe regeneration steps of the Calvin Cycleuse ATP to regenerate RUBP from some ofthe glyceraldehyde-3-P so the cyclecan continue.
Some of the carbohydrate is converted backinto ribulose 1,5 bisphosphate, the initial CO2
receptor molecule.
Fig. 8.3 (partial) - the regeneration steps
Height (m)-related variation in foliar structure in redwood.
“shade” leaves
“sun” leaves