Chapter 7 How Cells Release Chemical energy - 7 How Cells Release Chemical energy. ... Respiration Produces ATP under ... 4 ATP (2net) 32 ATP 2 NADH 8 NADH, 2 FADH 2 2 pyruvate

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  • Chapter 7Chapter 7

    How Cells Release How Cells Release Chemical energyChemical energy

  • Overview of Overview of Carbohydrate Breakdown PathwayCarbohydrate Breakdown Pathway

    Plants and all other photoautotrophs get Plants and all other photoautotrophs get energy from the sun, heterotrophs get by energy from the sun, heterotrophs get by eating plants and one anothereating plants and one another

    ATP is a common energy currency that ATP is a common energy currency that drives metabolic reactions in cellsdrives metabolic reactions in cells

  • Pathways of Carbohydrate Pathways of Carbohydrate BreakdownBreakdown

    Starts withStarts with glycolysis in the cytoplasmglycolysis in the cytoplasm Convert glucose and other sugars to pyruvateConvert glucose and other sugars to pyruvate

  • Comparison of main pathwaysComparison of main pathways

    Fermentation Fermentation pathwaypathway

    Aerobic Aerobic RespirationRespiration

    Produces ATP under Produces ATP under anaerobic conditionsanaerobic conditions

    Ends in cytoplasm, do Ends in cytoplasm, do not use oxygen, yields 2 not use oxygen, yields 2 ATP per molecule of ATP per molecule of glucoseglucose

    Produces ATP by Produces ATP by using oxygenusing oxygen

    Ends in mitochondria, Ends in mitochondria, uses oxygen, yields up uses oxygen, yields up to 36 ATP per glucose to 36 ATP per glucose moleculemolecule

    Oxygen acts as the Oxygen acts as the final acceptor of final acceptor of electrons used during electrons used during these reactionsthese reactions

  • Overview of Aerobic RespirationOverview of Aerobic Respiration

    Three main stages of aerobic respiration:Three main stages of aerobic respiration:1. Glycolysis1. Glycolysis

    2. Krebs cycle2. Krebs cycle

    3. Electron transfer phosphorylation3. Electron transfer phosphorylation

    Summary equation:Summary equation:

    CC66HH1212OO66 + 6O+ 6O22 6CO6CO22 + 6 H+ 6 H22OOglucose

  • Cytoplasm

    GLYCOLYSIS

    KrebsCycle ATP

    ATP

    6CO2

    4 ATP(2net)

    32 ATP

    2 NADH

    8 NADH, 2 FADH2

    2 pyruvate

    oxygen

    2 ATP

    glucose

    ATPATP

    2 ATP

    Electron TransferPhosphorylation

    Mitochondrion

    The first stage, glycolysis, occurs in the cells cytoplasm. Enzymes convert a glucose molecule to 2 pyruvate for a net yield of 2 ATP. During the reactions, 2 NAD+ pick up electrons and hydrogen atoms, so 2 NADH form.

    The second stage, the Krebs cycle and a few steps before it, occurs inside mitochondria. The 2 pyruvates are broken down to CO2, which leaves the cell. During the reactions, 8 NAD+ and 2 FAD pick up electrons and hydrogen atoms, so 8 NADH and 2 FADH2 form. 2 ATP also form.

    The third and final stage, electron transfer phosphorylation, occurs inside mitochondria. 10 NADH and 2 FADH2 donate electrons and hydrogen ions at electron transfer chains.Electron flow through the chains sets up H+ gradients that drive ATP formation. Oxygen

  • Overview of aerobic respirationOverview of aerobic respiration

  • Glycolysis Glycolysis Glucose Breakdown StartsGlucose Breakdown Starts

    First step First step Conversion of glucose to Conversion of glucose to pyruvatepyruvateEnzymes of glycolysis use two ATP to Enzymes of glycolysis use two ATP to convert one molecule of glucose to two convert one molecule of glucose to two molecules of threemolecules of three--carbon pyruvate carbon pyruvate

    Reactions transfer electrons and hydrogen Reactions transfer electrons and hydrogen atoms to two NADatoms to two NAD++ (reduces to NADH) (reduces to NADH)

    2 ATP is formed by substrate2 ATP is formed by substrate--level level phosphorylationphosphorylation

  • Products of GlycolysisProducts of Glycolysis

    Net yield of glycolysis:Net yield of glycolysis: 2 pyruvate, 2 ATP, and 2 NADH per glucose2 pyruvate, 2 ATP, and 2 NADH per glucose

    Pyruvate may: Pyruvate may: Enter fermentation pathways in cytoplasm Enter fermentation pathways in cytoplasm

    Enter mitochondria and be broken down Enter mitochondria and be broken down further in aerobic respirationfurther in aerobic respiration

  • ATP

    ATP

    glucose

    ADP

    ADP

    P

    Pglucose6phosphate

    fructose1,6bisphosphate

    Glycolysis

    ATP Requiring Steps

    p

  • ATP

    2 ADP

    2 NAD+ + 2 Pi

    2 PGA

    NADH

    2 PGAL

    ATP

    2 pyruvate

    2 PEP

    2 ADP

    to second stage Net 2 ATP + 2 NADH

    2 ATP producedby substrate-levelphosphorylation

    2 ATP producedby substrate-levelphosphorylation

    2 reduced coenzymes

    ATP Generating steps

  • Second Stage of Aerobic Second Stage of Aerobic RespirationRespiration

    Krebs CycleKrebs CycleBreak down of pyruvate to Carbon dioxideBreak down of pyruvate to Carbon dioxide

    The second stage of aerobic respiration The second stage of aerobic respiration takes place in the inner compartment of takes place in the inner compartment of mitochondria mitochondria

    It starts with acetylIt starts with acetyl--CoA formation and CoA formation and proceeds through the Krebs cycleproceeds through the Krebs cycle

  • outer mitochondrialcompartment (inbetween the twomembranes)

    inner mitochondrialcompartment

    inner membrane

    outer membrane(next to cytoplasm)

    KrebsCycle

    2 acetylCoA Breakdown of 2 pyruvate to 6CO2 yields 2 ATP. Also, 10 coenzymes are reduced (8 NADH, 2 FADH2). The coenzymes carry hydrogenions and electrons to sites of the third stage of aerobic respiration.

    INNER COMPARTMENT

    OUTER COMPARTMENT

    2 pyruvate(glycolysis)

    glucose

    b The second stage starts after membrane proteins transport pyruvate from the cytoplasm, across both mitochondrial membranes, to the innercompartment. Six carbon atoms enter these reactions (in two pyruvate), and six leave (in six CO2). Many coenzymes form.

    a An inner membrane divides a mitochondrions interior into two compartments. The second and third stages of aerobic respiration take place at this membrane.

    FADH2

    NADH

    ATPCO2

  • AcetylAcetyl--CoA FormationCoA Formation

    Two pyruvates from glycolysis are Two pyruvates from glycolysis are converted to two acetylconverted to two acetyl--CoA CoA

    Two COTwo CO22 leave the cellleave the cell

    AcetylAcetyl--CoA enters the Krebs cycle CoA enters the Krebs cycle

  • Krebs CycleKrebs Cycle

    In each turn of the Krebs cycle, one acetylIn each turn of the Krebs cycle, one acetyl--CoA is converted to two molecules of COCoA is converted to two molecules of CO22

    After two cyclesAfter two cycles Two pyruvates are dismantledTwo pyruvates are dismantled

    Glucose molecule that entered glycolysis is Glucose molecule that entered glycolysis is fully broken downfully broken down

  • Energy ProductsEnergy Products

    Reactions transfer electrons and hydrogen Reactions transfer electrons and hydrogen atoms to NADatoms to NAD++ and FADand FAD Reduced to NADH and FADHReduced to NADH and FADH22

    ATP forms by substrateATP forms by substrate--level level phosphorylationphosphorylation Direct transfer of a phosphate group from a Direct transfer of a phosphate group from a

    reaction intermediate to ADPreaction intermediate to ADP

  • Net ResultsNet Results

    Second stage of aerobic respiration results inSecond stage of aerobic respiration results in

    Six COSix CO22, two ATP, eight NADH, and two FADH, two ATP, eight NADH, and two FADH22for every two pyruvates for every two pyruvates

    Adding the yield from glycolysis, the total isAdding the yield from glycolysis, the total is

    Twelve reduced coenzymes and four ATP for Twelve reduced coenzymes and four ATP for each glucose moleculeeach glucose molecule

    Coenzymes deliver electrons and hydrogen to Coenzymes deliver electrons and hydrogen to the third stage of reactionthe third stage of reaction

  • NADH

    NADH

    FADH2

    ATP

    KrebsCycle

    KrebsCycle

    NADH

    NADH

    coenzyme A

    coenzyme A

    acetylCoA

    oxaloacetate citrate

    pyruvate

    AcetylCoAFormation

    CO2

    CO2NAD+

    NAD+

    NAD+

    FAD

    NAD+

    CO2

    ADP + P i

  • Third Stage: Aerobic RespirationThird Stage: Aerobic Respirations s Big Energy PayoffBig Energy Payoff

    Coenzymes deliver electrons and hydrogen ions Coenzymes deliver electrons and hydrogen ions to electron transfer chains in the inner to electron transfer chains in the inner mitochondrial membrane mitochondrial membrane Energy released by electrons flowing through Energy released by electrons flowing through the transfer chains moves Hthe transfer chains moves H++ from the inner to from the inner to the outer compartmentthe outer compartmentHH++ gradient builds up across the inner gradient builds up across the inner membranemembraneHH++ ions flow by concentration gradient back to ions flow by concentration gradient back to the inner compartment through ATP synthasesthe inner compartment through ATP synthases

  • The Aerobic Part of Aerobic The Aerobic Part of Aerobic RespirationRespiration

    At the end of electron transfer chain At the end of electron transfer chain oxygen and Hoxygen and H++ , forming water, forming water

    Overall, aerobic respiration yields up to 36 Overall, aerobic respiration yields up to 36 ATP for each glucose moleculeATP for each glucose molecule

  • KrebsCycle

    Glycolysis

    glucose

    youarehere

    Electron TransferPhosphorylation

  • NADHFADH2

    ATPADP + P i

    H+

    H+H+

    H+H+

    H+H+H+H+

    H+ H+ H+

    INNERMITOCHONDRIAL

    MEMBRANE

    OUTERCOMPARTMENT

    INNERCOMPARTMENT

    H2O

    1/2 O2

    H+

  • glucose

    Glycolysis

    2 pyruvate

    KrebsCycle

    Electron TransferPhosphorylation

    (2 net)

    2 NADH

    ATP

    2 FADH2

    6 NADH

    2 acetyl-CoA

    32

    ADP + P i

    H+

    ATP

    2 NADH

    2 NADH

    ATP

    ATP

    H+ H+ H+ H+

    2 NAD+

    2 CO2

    4 CO2

    2

    oxygen

    INNER MITOCHONDRIALCOMPARTMENT

    OUTER MITOCHONDRIALCOMPARTMENT

    CYTOPLASM

    water

    2

  • Anaerobic Anaerobic EnergyEnergy--Releasing PathwaysReleasing Pathways

    Fermentation PathwayFermentation PathwayBegins with glycolysis and ends in the Begins with glycolysis and ends in the cytoplasmcytoplasmDo not use oxygen or electron transfer Do not use oxygen or electron transfer chainschainsTwo ATP is formed from glycolysisTwo ATP is formed from glycolysisFinal steps do not produce ATP; only Final steps do not produce ATP; only regenerate oxidized NADregenerate oxidized NAD++ required for required for glycolysis to continueglycolysis to continue

  • FermentationPathway

    Glycolysis

    glucose

    you arehere

  • Anaerobic PathwaysAnaerobic Pathways

    Alcoholic fermentationAlcoholic fermentation

    End product:End product: Ethyl alcohol (or ethanol)Ethyl alcohol (or ethanol)

    Pyruvate(3 carbon) is broken downPyruvate(3 carbon) is broken down

    Enzyme splits pyruvate into two Enzyme splits pyruvate into two -- carbon carbon acetaldehyde and carbon dioxideacetaldehyde and carbon dioxide

  • Alcoholic fermentationAlcoholic fermentation

    Role of Yeast in fermentationRole of Yeast in fermentation

    They are unicellular fungiThey are unicellular fungi

    Sacchromyces cerevisiae Sacchromyces cerevisiae (Baker(Bakers yeast)s yeast)

    Cells release carbon dioxide in Cells release carbon dioxide in fementation and dough expandsfementation and dough expands

    Other strains are used in the production of Other strains are used in the production of winewine

  • Alcoholic FermentationAlcoholic Fermentation

  • Anaerobic PathwaysAnaerobic Pathways

    Lactate fermentationLactate fermentation

    End product:End product: LactateLactate

    Conversion of pyruvate into three carbon Conversion of pyruvate into three carbon lactate (lactic acid)lactate (lactic acid)

    Fermenters such as Fermenters such as lactobacillus lactobacillus acidophillusacidophillus can ferment milk, butter milk, can ferment milk, butter milk, cheese, yogurtcheese, yogurt

  • glucoseGlycolysis

    2

    pyruvate

    NADH

    2 NAD+

    2ATP

    ATP4

    NADH

    2 NAD+

    2

    LactateFermentation

    lactate

  • The TwitchersThe Twitchers

    SlowSlow--twitch and fasttwitch and fast--twitch skeletal muscle twitch skeletal muscle fibers can support different activity levels fibers can support different activity levels

    Aerobic respiration and lactate Aerobic respiration and lactate fermentation proceed in different fibers of fermentation proceed in different fibers of musclesmuscles

    These pathways yeilds ATP for musclesThese pathways yeilds ATP for muscles

  • Alternative Energy SourcesAlternative Energy Sources

    Complex Carbohydrate break downComplex Carbohydrate break downThey are broken down into simple sugars like They are broken down into simple sugars like glucoseglucoseGlucose gets converted to glucoseGlucose gets converted to glucose--66--phosphate.phosphate.If the body doesnIf the body doesnt need glucose for t need glucose for energy,glucoseenergy,glucose--66--phosphate can be converted phosphate can be converted to glycogen for storageto glycogen for storageWhen blood sugar drops, glycogen is converted When blood sugar drops, glycogen is converted to glucoseto glucose--66--phosphate and and enters the phosphate and and enters the glycolysis pathwayglycolysis pathway

  • Alternative Energy Sources;Alternative Energy Sources;Energy from FatsEnergy from Fats

    Most fat in the body are triglyceridesMost fat in the body are triglyceridesEnzymes convert fat into glycerol and fatty Enzymes convert fat into glycerol and fatty acidacidGlycerol is converted into PGAL, an Glycerol is converted into PGAL, an intermediate of glycolysisintermediate of glycolysisThe carbon back bones of the fatty acid The carbon back bones of the fatty acid tail is broken apart, and fragments are tail is broken apart, and fragments are converted into acetyl CoA, which can enter converted into acetyl CoA, which can enter the Krebs cyclethe Krebs cycle

  • Energy from ProteinsEnergy from Proteins

    Enzymes split proteins into amino acid Enzymes split proteins into amino acid subunitssubunits

    The amino group is removed and The amino group is removed and becomes ammonia, then ureabecomes ammonia, then urea

    Urea is excretedUrea is excreted

    Carbon Back bones can enter at several Carbon Back bones can enter at several different points of Krebs cycledifferent points of Krebs cycle

  • FOOD

    fats COMPLEX CARBOHYDRATES PROTEINS

    glucose, other simple sugars amino acids

    Glycolysis

    glycerolfatty acids

    pyruvate

    acetyl-coA

    NADH

    KrebsCycle

    NADH, FADH2

    PGALacetyl-coA

    oxaloacetateor anotherintermediateof the Krebs

    Electron TransferPhosphorylation

  • LifeLifes Unitys Unity

    Photosynthesis and aerobic respiration are Photosynthesis and aerobic respiration are interconnected on a global scale interconnected on a global scale

    In its organization, diversity, and continuity In its organization, diversity, and continuity through generations, life shows unity at through generations, life shows unity at the bioenergetic and molecular levelsthe bioenergetic and molecular levels

  • Driven by energy input from the sun, electrons and hydrogen are used to form ATP. ATP energy drives the synthesis of glucose from hydrogen, electrons (delivered by coenzymes), and carbon dioxides atoms.

    Photosynthesis Aerobic Respiration

    Energy input from two ATPinitiates three stages ofreactions. Many ATP form during thecomplete breakdown ofglucose to carbon dioxideand water.

    energy out (heat)

    chemical energy in many ATP available to drive nearly all cellular tasks

    carbondioxide,water

    glucose(storedchemicalenergy)

    oxygen

    energy out (heat)

    sunlightenergy in

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