10 Cellular Respiration

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<p>Slide 1</p> <p>Chapter 9</p> <p>Cellular RespirationSome intermediates feed into other pathwaysCatabolic pathways provide building block molecules and energy for anabolic pathwaysMetabolic Pathways</p> <p>energyenergyParticipants in Metabolic Pathways</p> <p>NAD+hexokinasephosphoglucose isomerasephosphofructokinaseReactant (substrate)IntermediatesProductParticipants in Metabolic Pathways</p> <p>NAD+hexokinasephosphoglucose isomerasephosphofructokinaseEnzymesCofactorsCoenzymesCellular Respiration &amp; Photosynthesis</p> <p>PHOTOSYNTHESISenergy-capturingCELLULAR RESPIRATIONenergy-releasing6O2 + 6CO2 + 6H2OSOLARENERGYC6H12O6ATPchemical energyglucoseWhich process is exergonic?</p> <p>Which process is anabolic?Glucose:Hub of Energy Processing in Cells</p> <p>Glucose production (anabolism) and storage</p> <p>Glucose:Hub of Energy Processing in Cells</p> <p>Breakdown of glucose (catabolism) for energyCellular RespirationCellular Respiration process by which cells produce ATP from a nutrient molecule (usually glucose) with high potential energyStep-wise release of energy from glucoseRequires O2Glucose is broken down (catabolized) to CO2 and H2OGlucose is oxidized to CO2Exergonic process (net)Released energy is used to make ATP (from ADP + Pi)</p> <p>4 connected pathwaysGlycolysisPyruvate processing (prep rxn)Citric acid (Krebs) cycleElectron transport chain/chemiosmosis2 types of electron carriers2 compartments2 types of ATP synthesisCell Respiration</p> <p>9ATP Cycle: Renewing Supplies of ATPEnergy from EXERGONIC reactions(e.g. cellular respiration)</p> <p>Energy for ENDERGONIC reactions(e.g. protein synthesis, muscle contraction)Making ATPATP is produced using the energy stored in organic molecules (chemical energy; potential energy) such as glucose</p> <p>One way of transferring energy is through the transfer of electronsElectrons and energy transferred to molecule BMethods of Producing ATPSubstrate-Level Phosphorylation enzyme catalyzes transfer of phosphate group from phosphorylated substrate to ADP (to make ATP)</p> <p>Oxidative Phosphorylation (Electron Transport &amp; Chemiosmosis) oxidation of NADH and FADH2 and electron transport produces proton gradient, which drives ATP synthesis (phosphorylation of ADP)</p> <p>EnzymeADPATPPhosphorylatedsubstrateMethods of Producing ATPsubstrate-level phosphorylationoxidative phosphorylation</p> <p>CytosolElectronsElectron transport chainGlycolysisSteps 1-3 (energy investment)Start with one glucose (hexose sugar) Rearrange structureAdd phosphate groupsSteps 4 &amp; 5 (sugar splitting)Split hexose in halfBoth halves used in subsequent rxnsSteps 6-10 (energy harvest)Rearrange structure &amp; remove phosphatesEnd with two pyruvates (3-carbon organic acid)</p> <p>Glycolysis What goes in and what comes out</p> <p>What comes out:What goes in:All 10 reactionsof glycolysisoccur in cytosolGlycolysis begins with anenergy-investmentphase: 2 ATP 2 ADPEnzymeGlucose-6-phosphateFructose-6-phosphateFructose-1,6-bisphosphateGlucose</p> <p>PyruvateThe 2 indicates that glucosehas been split into two 3-carbonsugars (only one is shown)During the energy payoff phase, 4 ATPare produced for a net gain of 2 ATPSubstrate-level phosphorylationsGlycolysis What goes in and what comes outGlycolysisTracking Carbon and EnergyCarbonInputs: 1 glucose (6-C)Outputs: 2 pyruvate (3-C each)</p> <p>EnergyInputs:potential energy contained in chemical bonds in glucose2 ATPOutputs:potential energy in bonds in pyruvate (less than in glucose)4 ATP (Net: 2 ATP)2 NADH (carry electrons/energy)Regulation of Glycolysis</p> <p>GlucoseGlucose-6-phosphateFructose-6-phosphateFructose-1,6-bisphosphatePFKCommitted Stepcatalyzed by phosphofructokinase (PFK)PFK is inhibited by ATPATPFeedback InhibitionFeedback Inhibition an enzyme in a metabolic pathway is inhibited by the product of the reaction sequence</p> <p>Why is feedback inhibition beneficial?</p> <p>AllostericsiteFructose-1,6-bisphosphateat active siteATP/ADP atactive siteRegulation of Glycolysis: PFK</p> <p>Fructose-6-phosphateFructose-1,6-bisphosphatePFKATPPFK has two binding sites for ATPActive site ATP as substrateAllosteric site ATP as allosteric inhibitorCellular Respiration or Fermentation?glucose2 pyruvate6 CO2 + 6 H2O2 ethanol + 2 CO2 or 2 lactateglycolysis2 ATPNo O2O2cellular respirationfermentation~25 ATPCellular Respiration or Fermentation?</p> <p>Cellular respirationIf electron acceptor(such as oxygen)is presentIf electron acceptor(such as oxygen)is NOT present</p> <p>Inefficient!Do not completely oxidize glucoseOnly utilize glycolysisOnly make 2 ATP per glucoseRegenerate NAD+</p> <p>Do not produce enough energy to sustain large, active, multicelled organisms</p> <p>Fermentation PathwaysFermentation PathwaysFirst step - GlycolysisGlucose 2 pyruvateGenerates 2 ATP and 2 NADH</p> <p>Lactic Acid Fermentation2 Pyruvate 2 LactateRegenerates 2 NAD+</p> <p>Alcoholic Fermentation2 Pyruvate 2 Ethanol (Ethyl Alcohol) + 2 CO2Regenerates 2 NAD+</p> <p>No intermediate;pyruvate acceptselectrons from NADH2 Acetylaldehyde2 Pyruvate2 Pyruvate2 Lactate2 EthanolPyruvate ProcessingInputs:2 Pyruvate2 Coenzyme A2 NAD+</p> <p>Outputs:2 Acetyl CoA2 NADH2 CO2</p> <p>Location: mitochondiral matrixPyruvate ProcessingCoenzyme A enzyme cofactor that acts as acetyl group carrierwhen acetyl group has bound CoA, it is activated (easily transferred to acceptor molecule)</p> <p>acetyl groupactivated</p> <p>Coenzyme APyruvate ProcessingTracking Carbon and EnergyCarbon:Inputs:2 pyruvate (3-C each)Outputs:2 acetyl groups (carried by Coenzyme A) (2-C each)2 CO2</p> <p>EnergyInputs:potential energy contained in bonds in pyruvateOutputs:potential energy in bonds in acetyl groups (carried by Coenzyme A)2 NADH (carry electrons/energy)Regulation of Pyruvate ProcessingPyruvate conversion to Acetyl CoA is catalyzed by the pyruvate dehydrogenase complex; key regulatory point in glucose oxidationInhibited by: (feedback inhibition)ATPAcetyl CoANADHActivated by:AMPCoANAD+</p> <p>pyruvate dehydrogenase complexCitric Acid CycleCitrate is oxidized in a step-wise mannerElectrons (energy) transferred to NAD+ and FAD</p> <p>Citric Acid CycleTracking Carbon and EnergyCarbon:Inputs:2 Acetyl groups (carried by Coenzyme A) (2-C each)Outputs:4 CO2</p> <p>EnergyInputs:potential energy contained in bonds of acetyl groupsOutputs:2 ATP (substrate-level ATP synthesis)6 NADH (carry electrons/energy)2 FADH2 (carry electrons/energy)So Farsummary of steps 1-3Glucose has been fully oxidized to 6 CO2Potential energy released from glucose has been used to generate 4 ATP (substrate-level ATP synthesis) andElectrons (energy) released from glucose during oxidation have been used to reduce:2 FAD 2 FADH210 NAD+ 10 NADHGlucose(reduced)6 CO2(oxidized)NAD+ and FADH(oxidized)NADH and FADH2(reduced)This is were the energy is!Cellular Respiration: Overview</p> <p>Electron Transport Chain and Chemiosmosis: SummaryElectrons (carried by NADH and FADH2) are delivered to the electron transport chain (ETC)Electrons are passed down the ETC to oxygen undergo redox reactions; release energyReleased energy is used to pump protons (H+) across inner mitochondrial membrane; generates a proton gradientEnergy in gradient (proton-motive force) is used to drive synthesis of ATP (via chemiosmosis) by ATP synthaseElectron Transport Chain - Overview</p> <p>Membraneof cristaeComplexIIntermembranespaceComplexIIMitochondrialmatrixComplex IComplex IIComplex IIIComplex IVComplexIIIComplexIVThe electron transportchain occurs in theinner membrane of themitochondrion(membranes of cristae)Chemiosmosis- Overview</p> <p>IntermembranespaceMitochondrialmatrixFo unitStatorRotorF1 unitElectron Transport ChainElectrons from NADH and FADH2 are passed down ETC to O2 (final electron acceptor); generates H+ gradient</p> <p>http://www.youtube.com/watch?v=xbJ0nbzt5Kw&amp;feature=related</p> <p>ChemiosmosisProton (H+) electrochemical gradient drives ATP synthesis via ATP synthaseProton-Motive Force Energy associated with movement of H+ ions down their concentration gradient across the IMM Chemiosmosis production of ATP via a proton gradient</p> <p>Cellular Respiration: Overview</p> <p>GlycolysisPyruvate Processing and Citric Acid CycleGlucoseAcetyl CoAPyruvateOxaloacetateIn each of these drops,energy is transferred toenergy-storing moleculesATP, NADH, and FADH2</p> <p>Series of chemical reactions, each catalyzed by a specific enzymeCellular respiration is a step-wise release of energy from glucoseDisruption of Chemiosmosis by PoisonsElectron Transport BlockersCyanideCO (carbon monoxide)UncouplerDNP (dinitrophenol)</p> <p>Disruption of Chemiosmosis by PoisonsElectron Transport BlockersCyanideCO (carbon monoxide)UncouplerDNP (dinitrophenol)</p> <p>Anaerobic RespirationWhat is the difference between anaerobic fermentation (previous slides) and anaerobic respiration?Anaerobic respiration involves the citric acid cycle and an electron transport chain, but this ETC uses a different final electron acceptor e.g. NO3- , SO42-, S, or Fe3+.Most species that perform anaerobic respiration are prokaryotes that live in environments devoid of O2.For more information, including the ecological and economic significance of these organisms, see Wikipedia: anaerobic respiration.Big Picture </p>