06 Respiration, Lithotrophy and Photolysis.pptx - Energy Transfer in Microbes • Metabolic degradation of organic molecules involves

06 Respiration, Lithotrophy and Photolysis.pptx - Energy...

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Energy Transfer in Microbes Metabolic degradation of organic molecules involves oxidation/reduction reactions This metabolic strategy is universal because Oxidation is exergonic!!
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If Δ E o < 0, then good electron donor If Δ E o > 0, then good electron acceptor
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Electron Transport Systems Electron transport systems are made up of a series of transfer molecules that accept electrons from donors and transfer them to acceptors, extracting oxidation energy to do work
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Electron Transport Systems Often, electron transport systems pump protons across membranes, generating: H + gradient (Δ[H + ]) pH gradient (ΔpH) Membrane potential (Δψ)
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Electron Transport Systems Often, electron transport systems pump protons across membranes, generating a proton-motive force
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Chemiosmotic Coupling The proton-motive force generated by ETS drives the synthesis of ATP Called chemiosmotic coupling Stoichiometry: 3 H+ through ATP synthase yields 1 ATP
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Chemiosmotic Coupling Chemiosmotic coupling also drives many other cellular functions in bacteria Solute transport Flagellar rotation
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Role of Oxygen in Respiration Oxygen is a strong oxidizing agent (electron acceptor) Glycolysis and the citric acid cycle produce a lot of reduced electron carriers (NADH and FADH 2 ) Transfer of electrons from NADH to oxygen could yield even more energy to do work because... Oxidation is exergonic!
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Bacterial Electron Transport Chain
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ATP Synthase ATP synthase is an enzyme that has a H + channel Energized protons go “screaming” through the channel, releasing energy The enzyme harnesses the proton- motive force to drive synthesis of ATP
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  • Spring '14
  • LawrenceR.Aaronson

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