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14 Cards in this Set
- Front
- Back
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What is chemolithotrophy? |
use of an inorganic chemical compound as an e- donor |
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What is a chemolithotroph? |
organism that uses oxidation & inorganic compounds to gain energy and e- many chemolithotrophs are autotrophs (Carbon source is CO2) & some are mixotrophs (carbon source is an organic compound) |
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How do chemolithotrophs achieve ATP synthesis & reducing power? |
--> ATP synthesis through oxidative phosphorylation (powered by PMF) -->Reducing power obtained either directly from inorganic compound or from reverse e- trasnport |
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How do we know if reverse electron flow is necessary? |
side note: Rxn has to have (+)dE for a (-)dG If e- donor has higher E'o than NAD+/ NADH, then organism will need to perform reverse e- flow to generate reducing equivalents |
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What makes Hydrogen an inorganic e- donor? |
- Some H2 oxidizers are anaerobes that couple H2 oxidation to reduction of nitrate, sulfite, ferric iron, etc. - Some H2 oxidizers are aerobes that uses O2 as terminal e- acceptor --- can also get carbon through carbon fixation BUT can also us organic carbon sources |
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What do sugars do? |
repress genes for H2 oxidation and carbon fixation |
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what is the e- flow in aerobic hydrogen oxidation? |
hydrogenase passes e- to quinone pool which are then passed to oxygen via cytochromes. (PMF generated contributes to ATP Synthesis) |
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what does cytoplasmic hydrogenase do? |
reduces NAD+ to NADH However NADH made this way can't contribute to PMF |
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What did Russian scientist learn by observing bacteria? |
H2S oxidized to So & when H2S is absent, So can serve as an energy source (inorganic e- donor) instead |
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What is the e- flow in oxidation of sulfur compounds? |
e- from sulfide and sulfite enter @ 2 different proteins. PMF generated as e- pass from Q pool to cyt bc1& during reduction of O2 e- from sulfite and sulfide @ higher reduction potential--> reverse e- flow is required |
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Why do we need to be cautious w/ iron oxidizing bacteria? |
Fe3+/ Fe2+ couple has different reduction potential @ different pH values ** At pH 2, oxygen = only viable e- acceptor b/c reduction potential is greater |
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What are FeOB? |
chemolithotrophs that use ferrous iron as energy source. its coupled to reduction of oxygen or nitrate. At nuetral pH, they can live w/ oxygen Or in anoxic/ microoxic environments At acidic pH, live in acid mine drainage systems |
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What's the e- flow in low- pH Fe2+ oxidation? |
done by OM cytochrome, iron stays extracellular. e- enter ETC via periplasmic e- carrier e- enter @ reduction potential greater that NAD+/NADH couple so reverse e- flow is needed |
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What happens during iron oxidation at neutral pH? |
Fe2+ directly reduces cyt c to intiate e- trasnport rxns making a PMF Reverse e- flow is needed to make NADH lots of iron needs to be oxidized b/c not very energy yielding oxidized iron is insoluble |
