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Published byMaximillian Hart Modified over 8 years ago
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Electron transport chains Electrons move from a carrier with a lower standard reduction potentials (E O ) to a carrier with a higher E O
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Mitochondrial electron transport chain Electrons eventually combine with 1/2 O 2 and 2 H + to form H 2 O Protons pumped across the membrane at various points during electron transport
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E. coli electron transport chain Electrons move from: NADH FAD Coenzyme Q Terminal oxidase varies depending on growth conditions Amount of protons pumped out depends on growth conditions
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P. denitrificans electron transport chains Has both aerobic and anaerobic electron transport chains Anaerobic chain uses NO 3 - as the final electron acceptor
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Oxidative phosphorylation Is dependent on the proton motive force and chemiosmosis
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The proton motive force Protons are pumped from the interior to the exterior of the membrane resulting in a gradient of protons and a membrane potential
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The roles of proton motive force Powers rotation of bacterial flagella Required for some types of active transport Generation of ATP
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The roles of proton motive force Flagella rotation Active transport
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Chemiosmosis Diffusion of protons back across the membrane drives the formation of ATP by ATP synthase
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ATP synthase Composed of 2 components: F 0 - membrane embedded F 1 - attached to inner membrane
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F 0 component Composed 1 a subunit, 2 b subunits and 9-12 c subunits Electrons pass through a channel in F 0 a subunit
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F 1 component Appears as a sphere on the inner membrane Composed of 3 subunits, 3 subunits 2 subunits and 1 subunit
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F 1 component Passage of electrons through F 0 causes subunit to rotate Rotation causes conformational changes in subunits that results in the synthesis of ATP
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F 1 component
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Yield of ATP in eukaryotic cells 1 NADH generates 2-3 ATPs 1 FADH 2 generates 2 ATPs Actual yield can be closer to 30 ATPs
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Yield of ATP in prokaryotic cells Prokaryotic cells generate less ATP Amounts vary depending on growth conditions
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Anaerobic respiration Final electron acceptor is an inorganic molecule other than oxygen Major electron acceptors are nitrate, sulfate and CO 2 Metals and certain organic molecules can also be reduced
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Anaerobic respiration Reduction of nitrate in respiration known as dissimilatory nitrate reduction Nitrate often reduced sequentially to nitrogen gas (N 2 ) Process referred to as denitrification
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Carbohydrate catabolism Glucose, fructose and mannose can enter glycolytic pathway after phosphorylation Galactose is modified before being transformed into glucose-6-P
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Carbohydrate catabolism Disaccharides and polysaccharides must be cleaved into monosaccharides Can be cleaved by hydrolysis or phosphorolysis (results in the addition of a phosphate group)
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Carbohydrate catabolism Reserve polymers like glycogen and starch are degraded by phosphorolysis to release glucose-1-P Converted to glucose-6-P and enters glycolytic pathway Poly- -hydroxybutyrate converted to acetyl-CoA and enters the TCA cycle
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Lipid catabolism Triacylglycerides are composed of glycerol and three fatty acids Lipases separate glycerol from fatty acids Glycerol phosphorylated and converted to dihydroxyacetone phosphate glyceraldehyde- 3-P glycolysis
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Lipid catabolism Fatty acids are converted to CoA esters and oxidized by the -oxidation pathway Fatty acids degraded to acetyl- CoA TCA cycle
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Lipid catabolism Fatty acids are converted to CoA esters and oxidized by the -oxidation pathway Fatty acids degraded to acetyl- CoA TCA cycle
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-oxidation pathway Produces 1.Acetyl-CoA 2.NADH 3.FADH 2
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Protein and amino acid catabolism Proteases hydrolyze proteins and polypeptides into amino acids Removal of amino group referred to as deamination
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Deamination Usually accomplished by transamination Amino group transferred to an -keto acid acceptor
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Deamination Organic acid oxidized for energy or used as carbon source
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Deamination Excess nitrogen excreted as ammonium ion
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Oxidation of inorganic molecules (chemolithotrophy) Chemolithotrophs derive energy from the oxidation of inorganic molecules Most common electron donors are hydrogen, reduced nitrogen compounds, reduced sulfur compounds and ferrous iron (Fe 2+ ) Oxygen, nitrate and sulfate can be used as the final electron acceptor
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Oxidation of inorganic molecules (chemolithotrophy)
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Hydrogen oxidation Several bacteria possess a hydrogenase enzyme that catalyzes the reaction: H 2 2H + + 2e - Electrons can be donated to an electron transport chain or NAD +
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Nitrogen oxidation Species of Nitrosomonas and Nitrosospira oxidize ammonia to nitrite NH 4 + + 3/2 O 2 NO 2 - + H 2 O + 2H + Species of Nitrobacter and Nitrococcus oxidize nitrite to nitrate NO 2 - + 1/2 O 2 NO 3 -
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Nitrogen oxidation Two genera working together can oxidize ammonia to nitrate NH 4 + + 2 O 2 NO 3 - Process referred to as nitrification
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Nitrogen oxidation Proton motive force can be used to produce ATP and NADH
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Sulfur oxidation Some microorganisms can use reduced sulfur compounds as a source of electrons Species of Thiobacillus oxidize sulfur-containing compounds to sulfuric acid (important environmental consequences)
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Sulfur oxidation Can generate ATP by oxidative phosphorylation and substrate level phosphorylation Substrate level phosphorylation requires the formation of adenosine 5-phosphosulfate (APS)
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Oxidation of inorganic molecules Much less energy is available from the oxidation of inorganic molecules than from the oxidation of organic molecules
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