Post on 05-Jan-2016
Photosynthesis
Biology 122
Genes and
Development
Cyanobacteria
Thylakoid membranes pack together to form grana from a spinach plant
Photosynthesis in Sulfur bacteria
Cyclic photophosphorylation
Enhancement effect of two wavelengths of light
Non-cyclic photophosphorylation
PhotosynthesisPhotosynthesis
Stroma
Thylakoid
(Lumen)
b6-f complex
Photosynthesis vs. ET/OxPhos
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
SCIENTIFIC THINKINGHypothesis: Photophosphorylation is coupled to electron transport by a proton gradient.
Prediction: If a proton gradient can be formed artificially, then isolated chloroplasts will phosphorylate ADP in the dark.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Spinach leaf
Dark conditions
Add
pH 4.0 pH 8.0
Assay forradioactive Pi
radioactive ATPADP +
SCIENTIFIC THINKING
Hypothesis: Photophosphorylation is coupled to electron transport by a proton gradient.
Prediction: If a proton gradient can be formed artificially, then isolated chloroplasts will phosphorylate ADP in the dark.
Test: Isolated chloroplasts are incubated in acid medium, then transferred in the dark to a basic medium to create an artificial
proton gradient.
Pi ATPATP
Pi
Isolatedchloroplasts
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Spinach leaf
Dark conditions
Add
pH 4.0 pH 8.0
Assay forradioactive Pi
radioactive ATPADP +
SCIENTIFIC THINKING
Hypothesis: Photophosphorylation is coupled to electron transport by a proton gradient.
Prediction: If a proton gradient can be formed artificially, then isolated chloroplasts will phosphorylate ADP in the dark.
Test: Isolated chloroplasts are incubated in acid medium, then transferred in the dark to a basic medium to create an artificial
proton gradient.
Result: Isolated chloroplasts can phosphorylate ADP in the dark as assayed by the incorporation of radioactive PO 4 into ATP.
Pi ATPATP
Pi
Isolatedchloroplasts
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Spinach leaf
Dark conditions
Add
pH 4.0 pH 8.0
Assay forradioactive Pi
radioactive ATPADP +
SCIENTIFIC THINKINGHypothesis: Photophosphorylation is coupled to electron transport by a proton gradient.
Prediction: If a proton gradient can be formed artificially, then isolated chloroplasts will phosphorylate ADP in the dark.
Test: Isolated chloroplasts are incubated in acid medium, then transferred in the dark to a basic medium to create an artificial
proton gradient.
Result: Isolated chloroplasts can phosphorylate ADP in the dark as assayed by the incorporation of radioactive PO 4 into ATP.
Conclusion: The energy from electron transport in the chloroplast is coupled to the phosphorylation of ADP by a proton gradient.
Pi ATPATP
Pi
Isolatedchloroplasts
TemperatureRegular temperature