In the light acidification of the lumen creates

In the light, acidification of the lumen creates a p. H gradient across thylakoid membranes. Fig 7. 22

Fig 7. 33 ATP-synthase is a protein motor Driving force is chemiosmotic gradient (Mitchell 1960 s)

Jagendorf experiment: Fig 7. 32 Acidified lumen drives ATP synthesis in dark

I. Overview How do herbicides that are inhibitors of electron transport activity work?

Some herbicides are inhibitors of electron transport Fig 7. 31 Blocks electron flow Intercepts electrons

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 Fig 7. 34 But they do have ATP-ase

Mitochondria also have electron transport chain and ATP synthase Fig 7. 34 Oxidative phosphorylation

of the Reactions Products Summary and substrates of Light and Dark reactions Substrate Energy Products Location source Light H 2 O light NADPH Thylakoids reactions ATP Dark reactions CO 2 NADPH Sugars ATP Stroma

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

The “dark” or Carbon Reduction Reactions Products and substrates of Light and Dark reactions Substrate Energy Products Location source Light H 2 O light NADPH Thylakoids reactions ATP Dark reactions CO 2 NADPH Carbo. ATP hydrates Stroma

Relating the Light and Dark Reactions Products and substrates of Light and Dark reactions Substrate Energy Products Location source Light H 2 O light NADPH Thylakoids reactions ATP Dark reactions CO 2 NADPH Carbo. ATP hydrates Stroma

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 C 3 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 “C 3” photosynthetic metabolism. C 4 photosynthesis - an adaptation to warm and dry environments CAM metabolism - an adaptation that greatly increases water use efficiency.

An outline of C 3 photosynthesis Fig. 8. 2 A 3 carbon molecule The Calvin Cycle (reductive pentose phosphate cycle) 3 Stages • Carboxylation • Reduction • Regeneration

Carboxylation • The key initial step in C 3 photosynthesis • RUBP + CO 2 ---> 3 -PGA • Catalyzed by “Rubisco”: ribulose 1, 5 -bisphosphate carboxylase-oxygenase • binds the 5 C RUBP molecule and 1 C CO 2, making two 3 C molecules. 5 C + 1 C -----> 2 x 3 C 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. 3 PGA + ATP + NADPH --> G 3 P can be used to make sucrose or starch

Fig. 8. 3 (partial) - the reduction steps

Fig. 8. 2 • Carboxylation • Reduction • Regeneration

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