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

Photosynthesis Stroma Thylakoid (Lumen)

b 6 -f complex

Photosynthesis vs. ET/OxPhos

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 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.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Spinach leaf Dark conditions Add pH 4.0pH 8.0 Assay for radioactive P i radioactive ATP ADP + 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. P i ATP P i Isolated chloroplasts

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Spinach leaf Dark conditions Add pH 4.0pH 8.0 Assay for radioactive P i radioactive ATP ADP + 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. P i ATP P i Isolated chloroplasts

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Spinach leaf Dark conditions Add pH 4.0pH 8.0 Assay for radioactive P i radioactive ATP ADP + 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. Conclusion: The energy from electron transport in the chloroplast is coupled to the phosphorylation of ADP by a proton gradient. P i ATP P i Isolated chloroplasts

 Temperature Regular temperature