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Lecture Note 10-17.docx

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Western University
Biology 1002B
Tom Haffie

Lecture 10Cellular RespirationCellular Respiration occurs in every living thing maybe not the whole path thoPhotosynthesis is the major process that fixes carbonCellular Respiration is the major path that converts it into energyMetabolic Pathways Catabolic Pathways G will be negative energy is released Not every individual step will have a negative GEx Cellular Respiration Exergonic Anabolic PathwaysG will be positive low energyhigh energy Not every individual step will have a positive GEx Photosynthesis EndergonicThese pathways have a number of steps with an overall goalATPADP CycleThe energy put in to form ATP is from a catabolic PathwayThe energy released from ATP is from a anabolic pathwayThis is the energy currency of the cellATP is the form of energy that cells useYou use the energy from catabolic pathways to drive anabolic pathwaysFood as FuelCH Bonds have lots of energy associated with themNeither are strongly electronegative electrons are easily stolenWe talk about glucose as it goes through the whole respiratory pathwayYou can break down fatty acidsproteins as wellCellular Respiration is a redox reactionRespiration is Controlled Combustion RespirationSmall activation energyEnzyme catalyzed reactionsEnergy is transferred to energy carriersDirect BurningLarge Activation Energy Required Note Either way the total possible energyAll Energy is released as heat nothing is stored that can be obtained is 686 KcalmolNAD as an electron shuttleThis is an electron shuttle moleculeCatabolic processes such as Respiration use NADAnabolic processes such as Photosynthesis use NADPThey are both 2 electron carriersThey do not fit into the same active siteH atom and 2 e from food are transferred to NAD Respiration Overview Glycolysis Pyruvate Oxidation Electron Transfer System GlucoseAcetylCoAOxidative Phosphorylation Pyruvate Citric Acid CycleATPWhere is it found and what does it doWhats at the start What about the endWhat is the change in potential energy in each of these stepsWhat steps require Oxygen WhyWhere is the carbon Where is it releasedGlycolysis I Energy InvestmentThe most ancient biochemical pathway in a cellOccurs in the cytosolEverything alive has glycolysis In the first step you are actually consuming ATPInteresting that we use ATP when the goal is to create ATP why phosphorylateThis makes the molecule more reactive glucose moleculeIt also places a negative charge on glucose which prevents it from passing through the membrane Glucose becomes stuckGlycolysis II Energy PayoffOne Molecule of Glucose gives two pyruvateYou make two NADH Four ATP and Two PyruvateTwo molecules of pyruvate have less free energy than glucoseSubstrate level phosphorylation one of two ways ATP is made o Transfer of phosphate group of substrate onto ATPNo requirement for oxygen This is an ancient pathwayPyruvate still holds energyLinking Glycolysis and the Citric Acid CycleGlycolysis occurs in the cytosol and pyruvate the end product is then transferred into the mitochondrial MatrixOnly Eukaryotic cells have a mitochondria but prokaryotes still use this pathwayYou cant equate cellular respiration with only eukaryotesThere is a decarboxylation reaction releases O as 2pyruvate crosses the membrane into the mitochondrial matrixThen an enzyme called Dehydrogenase removes a hydrogen to create an NADH
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