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Chapter 19 Photophosphorylation

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Chapter 19 Photophosphorylation Chapter 19 Part 3 Photophosphorylation Learning Goals: To Know 1. How energy of sunlight creates charge separation in the photosynthetic reaction complex and exciton transfer. 2. How electron transport is accompanied by the directional transport of protons across the membrane against their concentration gradient 3. Similarities and differences between plant-algal photosystems and bacterial photosystems. 4. How the electrochemical proton gradient drives synthesis of ATP by coupling the flow of protons via ATP synthase to conformational changes that favor formation of ATP in the active site 5. Roles of rhodopsins. Primary Production – Solar Energy Conversion Chloroplasts How do Photosynthetic Bacteria Fit in Here? Hill Reaction (driven by light) in Photophosphorylation 2 H2O + 2 A 2 AH2 + O2 “A” in Biological Systems = NADP+ so the Hill Reaction is: + + 2 H2O + 2 NADP 2 NADPH + 2H + O2 What Robert Hill in 1937 Actually Measured Was: The reduction of DCIP: going from blue to colorless. Electromagnetic Spectrum What is an Einstein? Light Energy Planck-Einstein Equation: E = h ν E = energy of a photon h = Planck’s Constant = 6.6 x 10-34 J.s v = vibration frequency ( of the wavelength of light; vibrational frequency increases with a decrease in wavelength ) In the text, E = hc/λ c/λ = v so red light, λ = 700 nm, c = 3x108m/s So that one red photon E = 2.83 x 10-19 J For an Einstein (a mole of photons) E = 168 kJ/einstein Chlorophyll a What is with the PINK ??? Phycobilins Carotenoids Photopigment Absorption Spectrum Chlorophyll Types Noon, Nov 18th: Surface Sun Light Spectra OE Pond Where is the Visible and Infra-red light ? Which one gets to the bottom? Noon, Nov 18th: Bottom The y-axis is in units of (einsteins/s)/m2 at each wavelength. Light Harvesting Complexes Have Many Chlorophylls Phycobilisome of Cyanobacteria Engleman Experiment (1882): Action Spectrum Light Harvesting – Energy Transfer to Reaction Center Solid State Photo-electron Transfer Two Bacterial Photosystems EOC Problem 28: Role of H2S in bacterial photosynthesis Purple Bacterial Reaction Center The Z Scheme is Both Linear and Circular EOC Problem 30 on electron flow between PS-I and PS-II. Photosystem II Photosystem I Trimer and Stripped Monomer Structure of PS I Electron and Proton Flow: Cyt-b6f Complex Cytochrome b6f Complex Pumps Protons Localization of PS1 and PS2 in Thylakoid Membrane Water Splitting Protein Utilizes all 5 Redox States of Mn Summary EOC Problem 41 on the Function of cyclic photophosphorylation. Comparison of Mitochondrion, Chloroplast, Bacteria Cytochrome b6f Complex Functions in Photophosphorylation AND Respiratory E-transport In Cyanobacteria Bacterial Rhodopsin – Becoming Ubiquitous Rhodopsin Proton Transfer: Cis -Trans Conformational Change Rhodopsins Are Becoming Recognized as Common There are 3 Classes of Rhodopsins: 1. Proton Pumping (previous example) – Halophilic Archaea. 2. Signal Transduction – Vision and Light/Dark Adaptions. 3. Chloride Pumping. They occur in Archaea, Bacteria and Eukarya - All Domains of Life To Know and Do Before Class • The energy of sunlight creates charge separation in the photosynthetic reaction complex and exciton transfer. • Stepwise electron transport is accompanied by the directional transport of protons across the membrane against their concentration gradient • Similarities and differences between plant-algal photosystems and bacterial photosystems. • The energy in the electrochemical proton gradient drives synthesis of ATP by coupling the flow of protons via ATP synthase to conformational changes that favor formation of ATP in the active site • Roles of rhodopsins. • EOC Problems: 28, 30, 31, 35, 41. .
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