2%20April%202009NutritionMetabolismPosting

2%20April%202009NutritionMetabolismPosting - Example: H2...

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Example: H 2 oxidizers Some chemolithotrophic bacteria can also do anaerobic respiration, (especially those that are H 2 oxidizers): 4 H 2 + 2 CO 2 2 CH 4 + 2 H 2 O Methanogens Source of e TEA Their type of metabolism allows them to inhabit places lacking O 2 . PRS: Can H 2 oxidizers be chemoheterotrophs? a. Yes b. No PRS: Nitrate reducers can be a) Only chemoheterotrophs b) Only chemolithotrophs c) Either heterotrophs or lithotrophs.
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PHOTOSYNTHESIS Conversion of light energy into chemical energy. Terms “aerobe”, “anaerobe” do not apply to photoautotrophs Instead use: oxygenic (e source is H 2 O; they produce O 2 during ATP synthesis) anoxygenic (e source is H 2 S or S o ; they produce S o or SO 4 –2 ; they are killed if O 2 is present)
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Photophosphorylation basics Photophosphorylation = light dependent ATP synthesis Similar to oxidative phosphorylation uses ETC (or alternative) uses membrane-bound ATPase to make ATP What differs: energy required to start redox reactions Absorption of light, not oxidation of a chemical In all cases there are Photosystems (PS) which are proteins/complexes in the membrane •absorb light •interact with electron transport proteins. 2 different photosystems in oxygenic phototrophs: PS II, PS I Only 1 photosystem PS in anoxygenic phototrophs.
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Photophosphorylation basics 3 different types of photophosphorylation - each type found in specific organisms. Proteins used are very different: Oxygenic photophosphorylation (the end products of this type of metabolism is ATP, NADPH – O 2 is a by- product). Anoxygenic photophosphorylation (the end products of this type of metabolism is ATP, NADPH – but O 2 is not a by-product). Bacteriorhodopsin-based (also anoxygenic, but does not employ usual photosystem or ETC)
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Oxygenic Photophosphorylation Happens in plants and a group of bacteria called cyanobacteria. One of the latter is prochlorococcus (40% of the photosynthetic cells in the ocean are this one species).
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How do oxygenic phototrophs work? Electrons have energy. 1. Light absorbed by PS II. Electron is ejected. 2. e moves into and through ETC, H + expelled leading to H + gradient needed to make ATP. 3. e transferred to PS I 4. PS I absorbs light and ejects e 5. e transferred to NADP + , reduces it to (NADPH + H + ). 6. H + gradient drives ATPase, ATP is made. Light Light H + ATP ADP +Pi NADP+ NADPH H + PSI Fe-Pr PS II ATP synthase H 2 O O 2 e- e- e- 1 6 5 4 3 2 H + 7 7. H 2 O replenishes e ejected from PS II. .
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How do oxygenic phototrophs work? Overall products of oxygenic photophosphorylation are ATP, NADPH and O 2 . All chemoheterotrophs/chemolithotrophs that require O 2 ( i.e. aerobes) depend on cells that can do oxygenic photophosphorylation releasing O 2 . All that oxygenic phototrophs require to make ATP and NADPH is light and H 2 O. They don’t need organic C or other inorganic molecules to provide electrons. So, they have “endless” resources.
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This note was uploaded on 11/03/2009 for the course ECON 210 taught by Professor James during the Spring '09 term at The University of British Columbia.

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2%20April%202009NutritionMetabolismPosting - Example: H2...

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