lecture_8-10_synopsis-2009

lecture_8-10_synopsis-2009 - MIC 140 Bacterial Physiology,...

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MIC 140 Bacterial Physiology, Lectures 8-10 10/12/09 Lecture 8, 9 & 10. Synopsis: Modes of membrane dependent ATP synthesis in bacteria. I. Approaches to the topic. 1. Mechanistic. Detailed proof of the thermodynamic limits; mathematical description of limits and mechanisms. Derivation of p = ∆Ψ -60 pH; i.e. Proton motive force = difference in electrical potential minus sixty times the difference in proton (hydrogen ion) concentration across a membrane. 2. Conceptual/comparative. Biochemical description of electron transport and vectoral proton translocation, variety of systems in bacteria. We will focus on this approach; there will be no mathematical proofs, but understanding of the limits is required, especially in the context of oxidation/reduction (redox) potential = electrode potential of the oxidized and reduced form of a compound or element: Eh = E o ’ + (RT/nF)ln[oxidized]/[reduced]). Redox Tower 3. Revisit trophic level classification in the context of electron donor and electron receiver, meaning of the language and illustration of diversity: organotroph, lithotroph and phototroph. II. Basic electron transport system (ETS). 1. Basic model of the most highly efficient ETS = mitochondria, Paracoccus spp, phototrophs. Three major multiprotein complexes that may or may not translocate protons, connected by mobile electron carriers: named based on organotrophy, we will change some names in litho- and phototrophy.
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MIC 140 Bacterial Physiology 10/12/09 DONOR membrane bound PROCESSOR extraneous membrane ACCEPTOR COMPLEX electron carrier COMPLEX electron carrier COMPLEX Also known as, in Paracoccus and mitochondrial organotrophy: NADH quinone cytochrome b/c cytochrome c cytochrome oxidase dehydrogenase 2. Contributions of the components to electron transport and proton translocation. a. Electron donor complex in organotrophy = NADH:quinol oxidoreductase. There are two types, one is capable of functioning as a proton pump thereby contributing to the p, the other is not. Stoichiometric assays imply 4 H + translocated per 2 e - = a “coupling” site. b. Quinone/quinol (reduced form). Whereas other components may vary, and even be absent, a lipophilic electron and proton carrying quinone (ubiquinone, menaquinone or plastoquinone) is present in all ETS. Quinone and Quinol are mobile by diffusion in membranes and move from the sites of reduction/oxidation to the sites of oxidation/reduction. c.
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lecture_8-10_synopsis-2009 - MIC 140 Bacterial Physiology,...

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