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CAMPBELL BIOLOGY Reece Urry Cain Wasserman Minorsky Jackson © 2014 Pearson Education, Inc. TENTH EDITION CAMPBELL BIOLOGY Reece Urry Cain Wasserman Minorsky Jackson TENTH EDITION Cellular Respiration and Fermentation Lecture Presentation by Nicole Tunbridge and Kathleen Fitzpatrick 9

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  • CAMPBELL

    BIOLOGYReece • Urry • Cain • Wasserman • Minorsky • Jackson

    © 2014 Pearson Education, Inc.

    TENTH

    EDITION

    CAMPBELL

    BIOLOGYReece • Urry • Cain • Wasserman • Minorsky • Jackson

    TENTH

    EDITION

    Cellular

    Respiration and

    Fermentation

    Lecture Presentation by

    Nicole Tunbridge and

    Kathleen Fitzpatrick

    9

  • © 2014 Pearson Education, Inc.

    Life Is Work

    Living cells

    require energy

    from outside

    sources

    Some animals,

    such as the

    giraffe, obtain

    energy by eating

    plants, and some

    animals feed on

    other organisms

    that eat plants

  • © 2014 Pearson Education, Inc.

    Energy flows into an

    ecosystem as sunlight

    and leaves as heat

    Photosynthesis

    generates O2 and

    organic molecules,

    which are used in

    cellular respiration

    Cells use chemical

    energy stored in organic

    molecules to generate

    ATP, which powers

    work

    Organicmolecules

    O2H2O+ +

  • © 2014 Pearson Education, Inc.

    Figure 9.2

    Lightenergy

    Organicmolecules

    O2CO2 H2O+

    Photosynthesisin chloroplasts

    Cellular respirationin mitochondria

    ECOSYSTEM

    ATP powersmost cellular work

    ATP

    Heatenergy

    +

  • © 2014 Pearson Education, Inc.

    BioFlix: The Carbon Cycle

  • © 2014 Pearson Education, Inc.

    Concept 9.1: Catabolic pathways yield energy by oxidizing organic fuels

    Catabolic pathways release stored energy by

    breaking down complex molecules

    carbohydrate, lipids and proteins

    Electron transfer plays a major role in these

    pathways

    OIL RIG

    Oxidation is lose electrons

    Reduction is gain electrons

  • © 2014 Pearson Education, Inc.

    Catabolic Pathways and Production of ATP

    The breakdown of organic molecules is exergonic*

    Releases energy

    Fermentation – anaerobic aka without O2

    Aerobic respiration – with O2

  • © 2014 Pearson Education, Inc.

    Cellular respiration – overall considered aerobic

    respiration

    Glucose derived from many sources via different

    enzymes

    But it is helpful to trace cellular respiration with the

    sugar glucose

    ***C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy (ATP + heat)

  • © 2014 Pearson Education, Inc.

    Redox Reactions: Oxidation and Reduction

    The transfer of electrons during chemical reactions

    releases energy stored in organic molecules

    This released energy is ultimately used to

    synthesize ATP

  • © 2014 Pearson Education, Inc.

    The Principle of Redox

    Chemical reactions that transfer electrons

    between reactants are called oxidation-reduction

    reactions, or redox reactions

    In oxidation, a substance loses electrons,

    or is oxidized

    In reduction, a substance gains electrons, or is

    reduced (the amount of positive charge is

    reduced)

  • © 2014 Pearson Education, Inc.

    Figure 9.UN01

    becomes oxidized

    (loses electron)

    becomes reduced

    (gains electron)

  • © 2014 Pearson Education, Inc.

    Figure 9.UN02

    becomes oxidized

    becomes reduced

  • © 2014 Pearson Education, Inc.

    The electron donor is called the reducing agent

    The electron receptor is called the oxidizing agent

    Some redox reactions do not transfer electrons but

    change the electron sharing in covalent bonds

    An example is the reaction between methane

    and O2

  • © 2014 Pearson Education, Inc.

    Figure 9.3

    Reactants Products

    Methane(reducing

    agent)

    Oxygen(oxidizing

    agent)

    Carbon dioxide Water

    becomes oxidized

    becomes reduced

  • © 2014 Pearson Education, Inc.

    Oxidation of Organic Fuel Molecules During Cellular Respiration

    During cellular respiration, the fuel (such as

    glucose) is oxidized, and O2 is reduced

  • © 2014 Pearson Education, Inc.

    Figure 9.UN03

    becomes oxidized

    becomes reduced

  • © 2014 Pearson Education, Inc.

    Stepwise Energy Harvest via NAD+ and the Electron Transport Chain

    In cellular respiration, glucose and other organic

    molecules are broken down in a series of steps

    Electrons from organic compounds are usually first

    transferred to NAD+, a coenzyme

    As an electron acceptor, NAD+ functions as an

    oxidizing agent during cellular respiration

    Each NADH (the reduced form of NAD+)

    represents stored energy that is tapped to

    synthesize ATP

  • © 2014 Pearson Education, Inc.

    Figure 9.4

    NAD+

    2 e− + 2 H+

    2[H](from food)

    Nicotinamide(oxidized form)

    Reduction of NAD+

    2 e− + H+

    NADH

    Nicotinamide(reduced form)

    Oxidation of NADHH+

    H+

    Dehydrogenase

  • © 2014 Pearson Education, Inc.

    Figure 9.4a

    NAD+

    Nicotinamide(oxidized form)

  • © 2014 Pearson Education, Inc.

    Figure 9.4b

    2 e− + 2 H+

    Reduction of NAD+

    2 e− + H+

    NADH

    Nicotinamide(reduced form)

    Oxidation of NADHH+

    H+

    Dehydrogenase

    2[H](from food)

  • © 2014 Pearson Education, Inc.

    Figure 9.UN04

    Dehydrogenase

  • © 2014 Pearson Education, Inc.

    NADH passes the electrons to the electron

    transport chain

    Unlike an uncontrolled reaction, the electron

    transport chain passes electrons in a series of

    steps instead of one explosive reaction

    O2 pulls electrons down the chain in an energy-

    yielding tumble

    The energy yielded is used to regenerate ATP

  • © 2014 Pearson Education, Inc.

    Figure 9.5

    H2 + ½ O2 2 H + ½ O2

    2 H+

    2 e−

    2 e−2 H+ +

    H2O

    ½ O2

    Controlledrelease of

    energy

    ATP

    ATP

    ATP

    Explosiverelease

    Cellular respirationUncontrolled reaction(a) (b)

    Fre

    e e

    nerg

    y,

    G

    Fre

    e e

    nerg

    y,

    G

    H2O

  • © 2014 Pearson Education, Inc.

    The Stages of Cellular Respiration: A Preview

    Harvesting of energy from glucose has three

    stages

    Glycolysis (breaks down glucose into two

    molecules of pyruvate)

    The citric acid cycle (completes the breakdown of

    glucose)

    Oxidative phosphorylation (accounts for most of

    the ATP synthesis)

  • © 2014 Pearson Education, Inc.

    Figure 9.UN05

    1.

    2.

    3.

    GLYCOLYSIS (color-coded blue throughout the chapter)

    PYRUVATE OXIDATION and the CITRIC ACID CYCLE

    (color-coded orange)

    OXIDATIVE PHOSPHORYLATION: Electron transport and

    chemiosmosis (color-coded purple)

  • © 2014 Pearson Education, Inc.

    Figure 9.6-1

    Electronsvia NADH

    ATP

    CYTOSOL MITOCHONDRION

    Substrate-level

    GLYCOLYSIS

    Glucose Pyruvate

  • © 2014 Pearson Education, Inc.

    Figure 9.6-2

    Electronsvia NADH

    Electronsvia NADH

    and FADH2

    ATP ATP

    CYTOSOL MITOCHONDRION

    Substrate-level Substrate-level

    GLYCOLYSIS PYRUVATEOXIDATION CITRIC

    ACIDCYCLEAcetyl CoAGlucose Pyruvate

  • © 2014 Pearson Education, Inc.

    Figure 9.6-3

    Electronsvia NADH

    Electronsvia NADH

    and FADH2

    ATP ATP ATP

    CYTOSOL MITOCHONDRION

    Substrate-level Substrate-level Oxidative

    GLYCOLYSIS PYRUVATEOXIDATION CITRIC

    ACIDCYCLE

    OXIDATIVEPHOSPHORYLATION

    (Electron transportand chemiosmosis)

    Acetyl CoAGlucose Pyruvate

  • © 2014 Pearson Education, Inc.

    BioFlix: Cellular Respiration

  • © 2014 Pearson Education, Inc.

    The process that generates most of the ATP is

    called oxidative phosphorylation because it is

    powered by redox reactions

  • © 2014 Pearson Education, Inc.

    Oxidative phosphorylation accounts for almost

    90% of the ATP generated by cellular respiration

    A smaller amount of ATP is formed in glycolysis

    and the citric acid cycle by substrate-level

    phosphorylation

    For each molecule of glucose degraded to CO2 and water by respiration, the cell makes up to 32

    molecules of ATP

  • © 2014 Pearson Education, Inc.

    Figure 9.7

    Enzyme Enzyme

    Substrate

    Product

    ATP

    ADP

    P

  • © 2014 Pearson Education, Inc.

    Concept 9.2: Glycolysis harvests chemical energy by oxidizing glucose to pyruvate

    Glycolysis (“sugar splitting”) breaks down glucose

    into two molecules of pyruvate

    Glycolysis occurs in the cytoplasm and has two

    major phases

    Energy investment phase

    Energy payoff phase

    Glycolysis occurs whether or not O2 is present

  • © 2014 Pearson Education, Inc.

    Figure 9.UN06

    GLYCOLYSISPYRUVATE

    OXIDATION

    CITRIC

    ACID

    CYCLE

    OXIDATIVE

    PHOSPHORYL-

    ATION

    ATP

  • © 2014 Pearson Education, Inc.

    Figure 9.8

    Energy Investment Phase

    Glucose

    Energy Payoff Phase

    Net

    2 ATP used 2 ADP + 2 P

    4 ADP + 4 P 4 ATP formed

    NAD+ 4 e−2 + + 4 H+ 2 H+2 NADH

    Pyruvate2

    2

    2

    2

    2

    2

    2

    2 H+H+

    4

    4

    Glucose Pyruvate

    ATPATP usedATP formed

    H2O

    NADH

    2 NAD+

    +

    +

    +

    ++ +

    2 H2O

    4e−

  • © 2014 Pearson Education, Inc.

    Figure 9.9a

    GLYCOLYSIS: Energy Investment Phase

    ADP

    Glucose6-phosphate

    Fructose6-phosphate

    ATP ATP

    ADP

    Glyceraldehyde3-phosphate (G3P)

    Fructose1,6-bisphosphate

    Dihydroxyacetonephosphate (DHAP)

    Glucose

    Hexokinase Phosphogluco-isomerase

    Phospho-fructokinase

    Aldolase

    Isomerase

    12

    5

    43

  • © 2014 Pearson Education, Inc.

    Figure 9.9aa-1

    GLYCOLYSIS: Energy Investment Phase

    Glucose

  • © 2014 Pearson Education, Inc.

    Figure 9.9aa-2

    GLYCOLYSIS: Energy Investment Phase

    Glucose6-phosphate

    ATP

    ADPGlucose

    Hexokinase

    1

  • © 2014 Pearson Education, Inc.

    Figure 9.9aa-3

    GLYCOLYSIS: Energy Investment Phase

    Glucose6-phosphate

    ATP

    ADPGlucose

    Hexokinase Phosphogluco-isomerase

    Fructose6-phosphate

    12

  • © 2014 Pearson Education, Inc.

    Figure 9.9ab-1

    GLYCOLYSIS: Energy Investment Phase

    Fructose6-phosphate

  • © 2014 Pearson Education, Inc.

    Figure 9.9ab-2

    GLYCOLYSIS: Energy Investment Phase

    3

    Fructose6-phosphate

    ATP

    ADP

    Fructose1,6-bisphosphate

    Phospho-fructokinase

  • © 2014 Pearson Education, Inc.

    Figure 9.9ab-3

    GLYCOLYSIS: Energy Investment Phase

    34

    5

    Fructose6-phosphate

    ATP

    ADP

    Glyceraldehyde3-phosphate (G3P)

    Fructose1,6-bisphosphate

    Dihydroxyacetonephosphate (DHAP)

    Phospho-fructokinase

    Aldolase

    Isomerase

  • © 2014 Pearson Education, Inc.

    Figure 9.9b

    GLYCOLYSIS: Energy Payoff Phase

    Glycer-

    aldehyde

    3-phosphate

    (G3P)

    Triose

    phosphate

    dehydrogenase

    6 1,3-Bisphospho-glycerate

    3-Phospho-

    glycerate

    2-Phospho-

    glycerate

    Phosphoenol-

    pyruvate (PEP)

    Pyruvate

    Phospho-

    glycerokinase

    Phospho-

    glyceromutase

    Enolase Pyruvate

    kinase

    2 NAD+

    7 89

    10

    2 NADH

    + 2 H+

    2

    2

    2

    2

    2 2 22

    2

    22 H2OATPATP

    ADPADP

  • © 2014 Pearson Education, Inc.

    Figure 9.9ba-1

    GLYCOLYSIS: Energy Payoff Phase

    4

    Glyceraldehyde

    3-phosphate (G3P)

    Dihydroxyacetone

    phosphate (DHAP)

    Aldolase

    Isomerase

    5

  • © 2014 Pearson Education, Inc.

    Figure 9.9ba-2

    GLYCOLYSIS: Energy Payoff Phase

    4

    Glyceraldehyde

    3-phosphate (G3P)

    Dihydroxyacetone

    phosphate (DHAP)

    Aldolase

    Isomerase

    5 6

    Triose

    phosphate

    dehydrogenase

    2 NAD+ 2 H+NADH

    2

    2

    2

    2

    1,3-Bisphospho-

    glycerate

  • © 2014 Pearson Education, Inc.

    Figure 9.9ba-3

    GLYCOLYSIS: Energy Payoff Phase

    4

    Glyceraldehyde

    3-phosphate (G3P)

    Dihydroxyacetone

    phosphate (DHAP)

    Aldolase

    Isomerase

    5 67

    Triose

    phosphate

    dehydrogenase

    2 NAD+ 2 H+NADH

    2

    2

    2

    2

    2 ADP

    1,3-Bisphospho-

    glycerate

    3-Phospho-

    glycerate

    Phospho-

    glycerokinase

    2

    2

    ATP

  • © 2014 Pearson Education, Inc.

    Figure 9.9bb-1

    3-Phospho-

    glycerate

    2

    GLYCOLYSIS: Energy Payoff Phase

  • © 2014 Pearson Education, Inc.

    Figure 9.9bb-2

    89

    Phospho-

    glyceromutase

    3-Phospho-

    glycerate

    2-Phospho-

    glycerate

    2 2 2

    Enolase

    Phosphoenol-

    pyruvate (PEP)

    2 H2O

    GLYCOLYSIS: Energy Payoff Phase

  • © 2014 Pearson Education, Inc.

    Figure 9.9bb-3

    89

    10

    Phospho-

    glyceromutase

    3-Phospho-

    glycerate

    2-Phospho-

    glycerate

    2 2 2

    Enolase

    Phosphoenol-

    pyruvate (PEP)

    Pyruvate

    Pyruvate

    kinase

    2

    2 ATPADP

    2 H2O2

    GLYCOLYSIS: Energy Payoff Phase

  • © 2014 Pearson Education, Inc.

    Concept 9.3: After pyruvate is oxidized, the citric acid cycle completes the energy-yielding oxidation of organic molecules

    In the presence of O2, pyruvate enters the

    mitochondrion (in eukaryotic cells) where the

    oxidation of glucose is completed

  • © 2014 Pearson Education, Inc.

    Oxidation of Pyruvate to Acetyl CoA

    Before the citric acid cycle can begin, pyruvate

    must be converted to acetyl Coenzyme A (acetyl

    CoA), which links glycolysis to the citric acid cycle

    This step is carried out by a multienzyme complex

    that catalyses three reactions

  • © 2014 Pearson Education, Inc.

    Figure 9.UN07

    GLYCOLYSISPYRUVATE

    OXIDATION

    CITRIC

    ACID

    CYCLE

    OXIDATIVE

    PHOSPHORYL-

    ATION

  • © 2014 Pearson Education, Inc.

    Figure 9.10

    CYTOSOL

    Pyruvate

    Transport protein

    MITOCHONDRION

    Acetyl CoANAD+ H+NADH +

    CO2Coenzyme A

    1

    2

    3

  • © 2014 Pearson Education, Inc.

    The Citric Acid Cycle

    The citric acid cycle, also called the Krebs cycle,

    completes the break down of pyruvate to CO2

    The cycle oxidizes organic fuel derived from

    pyruvate, generating 1 ATP, 3 NADH, and 1

    FADH2 per turn

  • © 2014 Pearson Education, Inc.

    Figure 9.11

    PYRUVATE OXIDATION

    Pyruvate (from glycolysis,

    2 molecules per glucose)

    NADH

    NAD+CO2

    CoA

    CoA

    + H+

    CoA

    CoA

    CO2

    CITRIC

    ACID

    CYCLE

    FADH2

    FAD

    ATP

    ADP + P i

    NAD+

    + 3 H+

    NADH3

    3

    2

    Acetyl CoA

  • © 2014 Pearson Education, Inc.

    Figure 9.11a

    PYRUVATE OXIDATION

    Pyruvate (from glycolysis,

    2 molecules per glucose)

    NADH

    NAD+CO2

    CoA

    CoA

    + H+ Acetyl CoA

  • © 2014 Pearson Education, Inc.

    Figure 9.11b

    CoA

    CoA

    CO2

    CITRIC

    ACID

    CYCLE

    FADH2

    FAD

    ATP

    ADP + P i

    NAD+

    + 3 H+

    NADH3

    3

    2

    Acetyl CoA

  • © 2014 Pearson Education, Inc.

    The citric acid cycle has eight steps, each

    catalyzed by a specific enzyme

    The acetyl group of acetyl CoA joins the cycle by

    combining with oxaloacetate, forming citrate

    The next seven steps decompose the citrate back

    to oxaloacetate, making the process a cycle

    The NADH and FADH2 produced by the cycle

    relay electrons extracted from food to the electron

    transport chain

  • © 2014 Pearson Education, Inc.

    Figure 9.UN08

    GLYCOLYSISPYRUVATE

    OXIDATION

    CITRIC

    ACID

    CYCLE

    OXIDATIVE

    PHOSPHORYL-

    ATION

    ATP

  • © 2014 Pearson Education, Inc.

    Figure 9.12-1

    Acetyl CoA

    Oxaloacetate

    CoA-SH

    Citrate

    CITRIC

    ACID

    CYCLE

    1

  • © 2014 Pearson Education, Inc.

    Figure 9.12-2

    Acetyl CoA

    H2O

    Oxaloacetate

    CoA-SH

    Citrate

    CITRIC

    ACID

    CYCLE

    Isocitrate

    1

    2

  • © 2014 Pearson Education, Inc.

    Figure 9.12-3

    Acetyl CoA

    H2O

    + H+

    Oxaloacetate

    CoA-SH

    Citrate

    -Ketoglutarate

    NAD+

    CO2

    NADHCITRIC

    ACID

    CYCLE

    Isocitrate

    1

    2

    3

  • © 2014 Pearson Education, Inc.

    Figure 9.12-4

    Acetyl CoA

    H2O

    + H+

    Oxaloacetate

    CoA-SH

    Citrate

    -Ketoglutarate

    CoA-SH

    NAD+

    CO2

    NADH

    CO2NAD+

    NADH

    + H+

    Succinyl

    CoA

    CITRIC

    ACID

    CYCLE

    Isocitrate

    1

    2

    4

    3

  • © 2014 Pearson Education, Inc.

    Figure 9.12-5

    Acetyl CoA

    H2O

    + H+

    Oxaloacetate

    CoA-SH

    Citrate

    -Ketoglutarate

    CoA-SH

    NAD+

    CO2

    NADH

    CO2NAD+

    NADH

    + H+

    Succinyl

    CoA

    ATP

    ADP

    GTP GDP

    Succinate

    CITRIC

    ACID

    CYCLE

    P i

    Isocitrate

    1

    2

    5

    4

    3

    CoA-SH

  • © 2014 Pearson Education, Inc.

    Figure 9.12-6

    Acetyl CoA

    H2O

    + H+

    Oxaloacetate

    CoA-SH

    Citrate

    -Ketoglutarate

    CoA-SH

    NAD+

    CO2

    NADH

    CO2NAD+

    NADH

    + H+

    Succinyl

    CoA

    ATP

    ADP

    GTP GDP

    Succinate

    FAD

    FADH2

    Fumarate

    CITRIC

    ACID

    CYCLE

    P i

    Isocitrate

    1

    2

    5

    64

    3

    CoA-SH

  • © 2014 Pearson Education, Inc.

    Figure 9.12-7

    Acetyl CoA

    H2O

    + H+

    Oxaloacetate

    CoA-SH

    Citrate

    -Ketoglutarate

    CoA-SH

    NAD+

    CO2

    NADH

    CO2NAD+

    NADH

    + H+

    Succinyl

    CoA

    ATP

    ADP

    GTP GDP

    Succinate

    FAD

    FADH2

    Fumarate

    H2O

    Malate

    CITRIC

    ACID

    CYCLE

    P i

    Isocitrate

    1

    2

    5

    64

    37

    CoA-SH

  • © 2014 Pearson Education, Inc.

    Figure 9.12-8

    Acetyl CoA

    H2O

    + H+

    Oxaloacetate

    CoA-SH

    Citrate

    -Ketoglutarate

    CoA-SH

    NAD+

    CO2

    NADH

    CO2NAD+

    NADH

    + H+

    Succinyl

    CoA

    ATP

    ADP

    GTP GDP

    Succinate

    FAD

    FADH2

    Fumarate

    H2O

    Malate

    CITRIC

    ACID

    CYCLE

    + H+

    NAD+

    P i

    NADH

    Isocitrate

    1

    2

    5

    64

    37

    8

    CoA-SH

  • © 2014 Pearson Education, Inc.

    Figure 9.12a

    Acetyl CoA

    Oxaloacetate

    CitrateIsocitrate

    H2O

    CoA-SH

    1

    2

  • © 2014 Pearson Education, Inc.

    Figure 9.12b

    3

    4-Ketoglutarate

    CO2

    NAD+

    NADH

    + H+

    CO2

    NAD+

    NADH

    + H+

    CoA-SH

    Isocitrate

    Succinyl

    CoA

  • © 2014 Pearson Education, Inc.

    Figure 9.12c

    Succinyl

    CoA

    6

    5

    Fumarate

    FADH2

    FAD

    Succinate

    GTP GDP

    ADP

    ATP

    P i

    CoA-SH

  • © 2014 Pearson Education, Inc.

    Figure 9.12d

    NADH

    Oxaloacetate

    Malate

    Fumarate

    H2O7

    8

    NAD+

    + H+

  • © 2014 Pearson Education, Inc.

    Concept 9.4: During oxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesis

    Following glycolysis and the citric acid cycle,

    NADH and FADH2 account for most of the energy

    extracted from food

    These two electron carriers donate electrons to

    the electron transport chain, which powers ATP

    synthesis via oxidative phosphorylation

  • © 2014 Pearson Education, Inc.

    The Pathway of Electron Transport

    The electron transport chain is in the inner

    membrane (cristae) of the mitochondrion

    Most of the chain’s components are proteins,

    which exist in multiprotein complexes

    The carriers alternate reduced and oxidized states

    as they accept and donate electrons

    Electrons drop in free energy as they go down the

    chain and are finally passed to O2, forming H2O

  • © 2014 Pearson Education, Inc.

    Figure 9.UN09

    GLYCOLYSISCITRIC

    ACID

    CYCLE

    PYRUVATE

    OXIDATION

    ATP

    OXIDATIVE

    PHOSPHORYL-

    ATION

  • © 2014 Pearson Education, Inc.

    Figure 9.13

    NADH

    e−2NAD+

    FADH2

    FAD2 e−

    FMN

    Fe•S

    Q

    Fe•S

    Cyt b

    Fe•S

    Cyt c1

    Cyt c

    Cyt a

    Cyt a3

    e−2

    (originally from

    NADH or FADH2)

    2 H+ + ½ O2

    H2O

    Multiprotein

    complexesI

    II

    III

    IV

    50

    40

    30

    20

    10

    0

    Fre

    e e

    nerg

    y (

    G)

    rela

    tive

    to

    O2

    (kc

    al/

    mo

    l)

  • © 2014 Pearson Education, Inc.

    Figure 9.13a

    50

    40

    30

    20

    10

    Fre

    e e

    ne

    rgy (

    G)

    rela

    tiv

    e t

    o O

    2(k

    ca

    l/m

    ol)

    NADH

    e−2NAD+

    FADH2

    Fe•S

    e−

    FMN

    Fe•S

    Q

    Cyt b

    FADI

    II

    FADMultiprotein

    complexes

    III

    Fe•S

    Cyt c1

    Cyt c

    Cyt a

    Cyt a3

    IV

    2

    e−2

  • © 2014 Pearson Education, Inc.

    Figure 9.13b

    30

    20

    10

    Fre

    e e

    nerg

    y (

    G)

    rela

    tive t

    o O

    2(k

    cal/m

    ol)

    0

    Cyt c1

    Cyt c

    Cyt a

    Cyt a3

    IV

    e−2

    2 H+ + ½ O2

    H2O

    (originally from

    NADH or FADH2)

  • © 2014 Pearson Education, Inc.

    Electrons are transferred from NADH or FADH2 to

    the electron transport chain

    Electrons are passed through a number of

    proteins including cytochromes (each with an iron

    atom) to O2

    The electron transport chain generates no ATP

    directly

    It breaks the large free-energy drop from food to

    O2 into smaller steps that release energy in

    manageable amounts

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    Chemiosmosis: The Energy-Coupling Mechanism

    Electron transfer in the electron transport chain

    causes proteins to pump H+ from the mitochondrial

    matrix to the intermembrane space

    H+ then moves back across the membrane,

    passing through the protein complex, ATP

    synthase

    ATP synthase uses the exergonic flow of H+ to

    drive phosphorylation of ATP

    This is an example of chemiosmosis, the use of

    energy in a H+ gradient to drive cellular work

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    Figure 9.14

    INTERMEMBRANE

    SPACERotor

    H+ Stator

    Internal rod

    Catalytic

    knob

    ADP+P i

    MITOCHONDRIAL

    MATRIX

    ATP

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    Video: ATP Synthase 3-D Structure, Top View

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    Video: ATP Synthase 3-D Structure, Side View

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    Figure 9.15

    Protein

    complex

    of electron

    carriers

    (carrying

    electrons

    from

    food)

    ATP

    synthase

    Electron transport chain Chemiosmosis

    Oxidative phosphorylation

    2 H+ + ½ O2 H2O

    ADP + P i

    H+

    ATP

    H+

    H+H+

    H+

    Cyt c

    Q

    I

    II

    III

    IV

    FADFADH2

    NADH NAD+

    1 2

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    Figure 9.15a

    Proteincomplexof electroncarriers

    2 H+ + ½ O2 H2O

    H+

    NAD+

    1

    H+

    H+

    NADH

    FADH2

    Cyt cCyt c

    IV

    III

    II

    I

    FAD

    (carryingelectronsfromfood) Electron transport chain

    Q

  • © 2014 Pearson Education, Inc.

    Figure 9.15b

    H+

    2

    H+

    ADP + P i ATP

    Chemiosmosis

    ATP

    synthase

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    The energy stored in a H+ gradient across a

    membrane couples the redox reactions of the

    electron transport chain to ATP synthesis

    The H+ gradient is referred to as a proton-motive

    force, emphasizing its capacity to do work

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    An Accounting of ATP Production by Cellular Respiration

    During cellular respiration, most energy flows in

    this sequence:

    glucose → NADH → electron transport chain →

    proton-motive force → ATP

    About 34% of the energy in a glucose molecule is

    transferred to ATP during cellular respiration,

    making about 32 ATP

    There are several reasons why the number of ATP

    is not known exactly

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    Figure 9.16

    Electron shuttles

    span membrane

    CYTOSOL2 NADH

    or

    2 FADH2

    2 NADH 2 FADH26 NADH

    MITOCHONDRION

    OXIDATIVE

    PHOSPHORYLATION

    (Electron transport

    and chemiosmosis)

    CITRIC

    ACID

    CYCLE

    PYRUVATE

    OXIDATION

    2 Acetyl CoA

    GLYCOLYSIS

    Glucose 2Pyruvate

    + 2 ATP + 2 ATP

    Maximum per glucose: About

    30 or 32 ATP

    + about 26 or 28 ATP

    2 NADH

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    Figure 9.16a

    Electron shuttles

    span membrane

    + 2 ATP

    2 NADHor

    2 FADH2

    GLYCOLYSIS

    Glucose 2Pyruvate

    2 NADH

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    Figure 9.16b

    2 FADH26 NADH

    CITRIC

    ACID

    CYCLE

    PYRUVATE

    OXIDATION

    2 Acetyl CoA

    + 2 ATP

    2 NADH

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    Figure 9.16c

    2 NADHor

    2 FADH2

    2 NADH 2 FADH26 NADH

    OXIDATIVE

    PHOSPHORYLATION

    (Electron transport

    and chemiosmosis)

    + about 26 or 28 ATP

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    Figure 9.16d

    Maximum per glucose: About

    30 or 32 ATP

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    Concept 9.5: Fermentation and anaerobic respiration enable cells to produce ATP without the use of oxygen

    Most cellular respiration requires O2 to produce

    ATP

    Without O2, the electron transport chain will cease

    to operate

    In that case, glycolysis couples with anaerobic

    respiration or fermentation to produce ATP

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    Anaerobic respiration uses an electron transport

    chain with a final electron acceptor other than O2,

    for example sulfate

    Fermentation uses substrate-level phosphorylation

    instead of an electron transport chain to generate

    ATP

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    Types of Fermentation

    Fermentation consists of glycolysis plus reactions

    that regenerate NAD+, which can be reused by

    glycolysis

    Two common types are alcohol fermentation and

    lactic acid fermentation

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    In alcohol fermentation, pyruvate is converted to

    ethanol in two steps

    The first step releases CO2

    The second step produces ethanol

    Alcohol fermentation by yeast is used in brewing,

    winemaking, and baking

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    Figure 9.17

    2 ADP + 2 P i 2 ATP

    Glucose

    2 NAD+ NADH2

    + 2 H+

    2 Pyruvate

    CO22

    2 Ethanol

    (a) Alcohol fermentation

    2 Acetaldehyde 2 Lactate

    Lactic acid fermentation

    2 ADP + 2 P i 2 ATP

    GLYCOLYSIS

    NAD+

    + 2 H+NADH22

    2 Pyruvate

    (b)

    GLYCOLYSIS Glucose

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    Figure 9.17a

    2 ADP + 2 P i

    NAD+

    + 2 H+

    GLYCOLYSISGlucose

    2 ATP

    22

    2 Ethanol 2 Acetaldehyde

    2 Pyruvate

    (a) Alcohol fermentation

    2 CO2NADH

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    Figure 9.17b

    2 ADP + 2 P i

    NAD+

    + 2 H+

    GLYCOLYSISGlucose

    2 ATP

    22

    Lactate

    (b) Lactic acid fermentation

    NADH

    2 Pyruvate

    2

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    Animation: Fermentation Overview

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    In lactic acid fermentation, pyruvate is reduced

    by NADH, forming lactate as an end product, with

    no release of CO2

    Lactic acid fermentation by some fungi and

    bacteria is used to make cheese and yogurt

    Human muscle cells use lactic acid fermentation to

    generate ATP when O2 is scarce

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    Comparing Fermentation with Anaerobic and Aerobic Respiration

    All use glycolysis (net ATP = 2) to oxidize glucose

    and harvest chemical energy of food

    In all three, NAD+ is the oxidizing agent that

    accepts electrons during glycolysis

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    The processes have different mechanisms for

    oxidizing NADH:

    In fermentation, an organic molecule (such as

    pyruvate or acetaldehyde) acts as a final electron

    acceptor

    In cellular respiration electrons are transferred to

    the electron transport chain

    Cellular respiration produces 32 ATP per glucose

    molecule; fermentation produces 2 ATP per

    glucose molecule

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    Obligate anaerobes carry out fermentation or

    anaerobic respiration and cannot survive in the

    presence of O2

    Yeast and many bacteria are facultative

    anaerobes, meaning that they can survive

    using either fermentation or cellular respiration

    In a facultative anaerobe, pyruvate is a fork in

    the metabolic road that leads to two alternative

    catabolic routes

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    Figure 9.18

    Glucose

    GlycolysisCYTOSOL

    Pyruvate

    No O2 present:

    Fermentation

    O2 present:

    Aerobic cellular

    respiration

    Ethanol,

    lactate, or

    other products

    MITOCHONDRION

    Acetyl CoA

    CITRIC

    ACID

    CYCLE

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    The Evolutionary Significance of Glycolysis

    Ancient prokaryotes are thought to have used

    glycolysis long before there was oxygen in the

    atmosphere

    Very little O2 was available in the atmosphere until

    about 2.7 billion years ago, so early prokaryotes

    likely used only glycolysis to generate ATP

    Glycolysis is a very ancient process

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    Concept 9.6: Glycolysis and the citric acid cycle connect to many other metabolic pathways

    Gycolysis and the citric acid cycle are major

    intersections to various catabolic and anabolic

    pathways

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    The Versatility of Catabolism

    Catabolic pathways funnel electrons from many

    kinds of organic molecules into cellular respiration

    Glycolysis accepts a wide range of carbohydrates

    Proteins must be digested to amino acids; amino

    groups can feed glycolysis or the citric acid cycle

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    Fats are digested to glycerol (used in glycolysis)

    and fatty acids (used in generating acetyl CoA)

    Fatty acids are broken down by beta oxidation

    and yield acetyl CoA

    An oxidized gram of fat produces more than twice

    as much ATP as an oxidized gram of carbohydrate

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    Figure 9.19-1

    Proteins Carbohydrates Fats

    Amino

    acidsSugars Glycerol Fatty

    acids

  • © 2014 Pearson Education, Inc.

    Figure 9.19-2

    Proteins Carbohydrates Fats

    Amino

    acidsSugars Glycerol Fatty

    acids

    GLYCOLYSIS

    Glucose

    Glyceraldehyde 3- P

    PyruvateNH3

  • © 2014 Pearson Education, Inc.

    Figure 9.19-3

    Proteins Carbohydrates Fats

    Amino

    acidsSugars Glycerol Fatty

    acids

    GLYCOLYSIS

    Glucose

    Glyceraldehyde 3- P

    Pyruvate

    Acetyl CoA

    NH3

  • © 2014 Pearson Education, Inc.

    Figure 9.19-4

    Proteins Carbohydrates Fats

    Amino

    acidsSugars Glycerol Fatty

    acids

    GLYCOLYSIS

    Glucose

    Glyceraldehyde 3- P

    Pyruvate

    Acetyl CoA

    CITRIC

    ACID

    CYCLE

    NH3

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    Figure 9.19-5

    Proteins Carbohydrates Fats

    Amino

    acidsSugars Glycerol Fatty

    acids

    GLYCOLYSIS

    Glucose

    Glyceraldehyde 3- P

    Pyruvate

    Acetyl CoA

    CITRIC

    ACID

    CYCLE

    OXIDATIVE

    PHOSPHORYLATION

    NH3

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    Biosynthesis (Anabolic Pathways)

    The body uses small molecules to build other

    substances

    These small molecules may come directly from

    food, from glycolysis, or from the citric acid cycle

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    Regulation of Cellular Respiration via Feedback Mechanisms

    Feedback inhibition is the most common

    mechanism for metabolic control

    If ATP concentration begins to drop, respiration

    speeds up; when there is plenty of ATP,

    respiration slows down

    Control of catabolism is based mainly on

    regulating the activity of enzymes at strategic

    points in the catabolic pathway

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    Figure 9.20

    Glucose

    AMP

    Stimulates

    GLYCOLYSIS

    Fructose 6-phosphate

    Phosphofructokinase

    Fructose 1,6-bisphosphateInhibits Inhibits

    Citrate

    Pyruvate

    Acetyl CoAATP

    CITRIC

    ACID

    CYCLE

    Oxidative

    phosphorylation

  • © 2014 Pearson Education, Inc.

    Figure 9.UN10a

  • © 2014 Pearson Education, Inc.

    Figure 9.UN10b

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    Figure 9.UN11

    Inputs Outputs

    Glucose 2 Pyruvate 2 2+ + NADHATP

    GLYCOLYSIS

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    Figure 9.UN12

    Inputs Outputs

    CITRIC

    ACID

    CYCLE

    2 Pyruvate 2 Acetyl CoA

    2 Oxaloacetate

    2

    26

    8

    FADH2

    NADHATP

    CO2

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    Figure 9.UN13

    INTERMEMBRANE

    SPACE

    Protein complex

    of electron

    carriers

    H+

    H+H+

    2 H+ + ½ O2 H2O

    MITOCHONDRIAL MATRIX

    (carrying electrons from food)

    NADH NAD+

    FADH2

    I

    II

    III

    IV

    Cyt c

    Q

    FAD

  • © 2014 Pearson Education, Inc.

    Figure 9.UN14

    INTER-

    MEMBRANE

    SPACE H+

    MITOCHON-

    DRIAL

    MATRIXATP

    synthase

    ADP + P i H+ ATP

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    Figure 9.UN15

    Low ATP

    concentration

    High ATP

    concentration

    Fructose 6-phosphate

    concentration

    Ph

    osp

    ho

    fru

    cto

    kin

    as

    e

    acti

    vit

    y

  • © 2014 Pearson Education, Inc.

    Figure 9.UN16

    pH

    dif

    fere

    nce

    acro

    ss m

    em

    bra

    ne

    Time

  • © 2014 Pearson Education, Inc.

    Figure 9.UN17