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

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 SubstrateEnergy source ProductsLocation Light reactions H2OH2OlightNADPH ATP Thylakoids Dark reactions CO 2 NADPH ATP SugarsStroma Summary of the Light Reactions

The Carbon Reaction of photosynthesis Using ATP and NADPH to produce carbohydrates from CO 2.

Products and substrates of Light and Dark reactions SubstrateEnergy source ProductsLocation Light reactions H2OH2OlightNADPH ATP Thylakoids Dark reactions CO 2 NADPH ATP Carbo- hydrates Stroma The “dark” or Carbon Reduction Reactions

Products and substrates of Light and Dark reactions SubstrateEnergy source ProductsLocation Light reactions H2OH2OlightNADPH ATP Thylakoids Dark reactions CO 2 NADPH ATP Carbo- hydrates Stroma Relating the Light and Dark Reactions

Photosynthesis: Carbon Reactions (Chapter 8) Photosynthetic CO 2 uptake uses the products of the light reactions to enable the “dark” or carbon reduction reactions.

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 reactions the Calvin cycle and C3 photosynthesis II. Photorespiration - a process of O 2 reduction that competes with CO 2 reduction and reduces the rate of carbon fixation. III. CO 2 concentrating mechanisms - variation on the “C3” photosynthetic metabolism. C4 photosynthesis - an adaptation to warm and dry environments CAM metabolism - an adaptation that greatly increases water use efficiency.

Fig. 8.2 The Calvin Cycle (reductive pentose phosphate cycle) 3 Stages Carboxylation Reduction Regeneration A 3 carbon molecule An outline of C3 photosynthesis

Carboxylation The key initial step in C3 photosynthesis RUBP + CO 2 ---> 3-PGA Catalyzed by “Rubisco”: ribulose 1,5-bisphosphate carboxylase-oxygenase binds the 5C RUBP molecule and 1C CO 2, 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

The regeneration steps of the Calvin Cycle use ATP to regenerate RUBP from some of the glyceraldehyde-3-P so the cycle can continue. Some of the carbohydrate is converted back into ribulose 1,5 bisphosphate, the initial CO 2 receptor molecule.

Fig. 8.3 (partial) - the regeneration steps

Height (m)-related variation in foliar structure in redwood. “shade” leaves “sun” leaves