Cell Respiration C 6 H 12 O 6 + 6 O 2 + 6 H 2 O  6 CO 2 + 12 H 2 O + ATP

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  • Cell RespirationC6H12O6 + 6 O2 + 6 H2O 6 CO2 + 12 H2O + ATP

  • Overview: 4 main processesGlycolysis

    Pyruvate oxidation

    Citric Acid Cycle

    Electron Transport Chain

  • GlycolysisSugar splitting 1 molecule of glucose (6-C) is split into 2 pyruvates (3-C)

    Occurs in cytosolATP, NAD+, and Pi float freely

    Series of reactions catalyzed by specific enzymes

  • 1st phase of Glycolysis is EndergonicRequires input of ATP

    Glucose is stable, not readily broken down

    2 phosphorylation rxns. transfer P from ATP to sugar fructose 1,6-biphosphate

  • Fructose 1,6-biphosphate broken down into 2 3-C molecules: dihydroxyacetone phosphate and glyceraldehyde-3-phosphate (G3P)

    Dihydroxyacetone phosphate converted to G3P

    OVERALL: Glucose + 2ATP 2 G3P + 2 ADP

  • 2nd phase of Glycolysis is ExergonicG3P is oxidized to produce NADH + H+

    Since 2 G3P, 2 NADH are produced (used later to produce ATP)

    Substrate-level phosphorylation- P is transferred from intermediate to ADP2x per G3PTotal of 4 ATP made

  • Glycolysis Summary:http://programs.northlandcollege.edu/biology/Biology1111/animations/glycolysis.html

    OVERALL REACTION:http://www.science.smith.edu/departments/Biology/Bio231/glycolysis.htmlGlucose + 2 ATP 2 pyruvate + 2NADH + 4 ATP (net gain of 2 ATP)

  • Remaining Processes occur in the Mitochondria

  • Pyruvate OxidationPyruvate enter mitochondria in eukaryotes

    Pyruvate Dehydrogenase catalyses oxidative decarboxylation Carboxyl removed as CO22-C fragment becomes oxidized creating NADH2-C acetyl group attached to coenzyme A

  • Overall:2 puruvate + 2 NAD+ + 2 CoA

    2 acetyl CoA + 2 NADH + 2 CO2

  • Citric Acid Cycle1st reaction: acetyl CoA transfers 2-C acetyl group to 4-C oxaloacetate to get citrateSeries of reactions:2 CO2 are removed yielding 4-C compoundOxidation occurs yielding 3 NADH and 1 FADH2 per acetyl coA1 ATP produced by substrate level phosphorylationOxaloacetate is regenerated

  • Citric Acid Cycle

  • Electron Transport ChainETC is series of electron carriers embedded in inner mitochondrial membrane of eukaryotes (plasma membrane of prokaryotes)

    Electrons produced during glycolysis, pyruvate oxidation, and Citric Acid Cycle enter ETC via carrier molecules

  • Overview of ETC:High energy electrons are passed along ETC in series of exergonic reactions

    Energy from these rxns. drives ATP synthesis (endergonic)

    This is oxidative phosphorylation result of redox rxns.

  • 3 of the 4 complexes are proton pumps pump H+ into the intermembrane space

    Complex I accepts e- from NADH and transfers it via ubiquinone (aka coenzyme Q) to Complex III

    Complex II accepts e- from FADH2 and transfers via ubiquinone

  • Complex III accepts e- from ubiquinone and transfers them via cytochrome c to Complex IV

    Final Electron acceptor is Oxygen (1/2 O2) it accepts 2 e- and combines with 2 protons to create water

    Aerobic respiration requires O2; without it as final e- acceptor, entire chain backs up

  • http://www.science.smith.edu/departments/Biology/Bio231/etc.html



  • ChemiosmosisETC is coupled to ATP synthesis by proton gradient

    Concentration of H+ in intermembrane space is much higher than matrix

    H+ diffuses down its gradient through ATP synthase - exergonic

  • Exergonic diffusion coupled to endergonic ATP synthesis




  • SO WHATS THE POINT??Glycolysis gives us 2 ATP (net) + 2 NADH

    Pyruvate oxidation 2 NADH + 2 CO2

    Citric Acid Cycle 2 ATP + 4 CO2 + 6 NADH + 2FADH2

  • ADDING UP ATPEach NADH yields 3 ATP, so Glycolysis 2 NADH 6 ATP**except for most eukaryotic cells which shuttle e- of NADH across mit. Mem., costing 1 ATP/NADH Pyruvate oxidation 2 NADH 6 ATPCitric Acid Cycle 6 NADH 18 ATP

    Each FADH2 yields 2 ATPCitric Acid Cycle 2 FADH2 4 ATP

  • GRAND TOTALSGlycolysis = 2 ATP

    Citric Acid Cycle = 2 ATP

    ETC = 32 34 ATP

    Aerobic Respiration = 36 38 ATP

  • Efficiency (i.e., thermodynamics)Burning glucose releases 686 kcal/mol heat

    Free energy in phosphate bonds of ATP = 7.6 kcal

    7.6 kcal/mol ATP x 36 ATP = 274 kcal/mol

    Efficiency of aerobic resp. = 274/686 = 40%Rest is lost as heat


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