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AP Biology Ms. Gaynor. Chapter 9 (Part 1): Cellular Respiration. Light energy. ECOSYSTEM. Photosynthesis in chloroplasts. Organic molecules. CO 2 + H 2 O. + O 2. Cellular respiration in mitochondria. ATP. powers most cellular work. Heat energy.

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Ap biology ms gaynor

AP BiologyMs. Gaynor

Chapter 9 (Part 1):

Cellular Respiration


Energy flows into ecosystems as sunlight and leaves as heat

Light energy

ECOSYSTEM

Photosynthesisin chloroplasts

Organicmolecules

CO2 + H2O

+ O2

Cellular respirationin mitochondria

ATP

powers most cellular work

Heatenergy

Energy Flows into ecosystems as sunlight and leaves as heat

http://wps.aw.com/bc_campbell_biology_7/


Ap biology ms gaynor

Carbon Cycle


Reminder

Reminder….

  • Anabolic pathways (“A” for add together)

    • Build molecules from simpler ones (ex: photosynthesis)

    • Consume energy (endergonic)

  • Catabolic pathways (“C” for cut in parts)

    • Break down complex molecules into simpler compounds (ex: cell respiration)

    • Release energy (exergonic)


Cellular respiration

Cellular respiration

  • Most efficient catabolic pathway

  • Consumes O2 and organic molecules (ex: glucose)

  • Yields ATP To keep working cells must regenerate ATP


Catabolic pathways yield energy by oxidizing organic fuels

Catabolic pathways yield energy by oxidizing organic fuels

  • The breakdown of organic molecules is exergonic

  • One catabolic process, fermentation

    • Is a partial degradation of sugars that occurs without oxygen

  • Another example is cellular respiration


Cellular respiration1

Cellular respiration

  • Occurs in mitochondria

    • similar to combustion of gas in an engine after O2 is mixed with hydrocarbon fuel.

      • Food = fuel for respiration.

      • The exhaust =CO2 and H2O.

        The overall process is:

        organic compounds + O2  CO2 + H2O + energy

        (ATP + heat)

    • Carbohydrates, fats, and proteins can all be used as the fuel, but most useful is glucose.


Mitochondria

Mitochondria

  • # of mito’s in a cell varies by organism & tissue type

  • has its own independent DNA (and ribosomes)  this DNA shows similarity to bacterial DNA

    • according to the endosymbiotic theory mitochondria (and chloroplasts) are descended from free-living prokaryotes.


Mitochondrion structure

Mitochondrion Structure


Mitochondrion structure1

Mitochondrion Structure

  • Outer membrane – similar to plasma membrane; contains integral proteins

  • Inner membrane- NOT permeable to ions (needs help to cross); there is a membrane potential across the inner membrane; contains ATP synthase

    • Cristae – large surface area due to folding

  • Matrix- gel-like in middle or lumen; many contains enzymes for cellular respiration


  • Recall redox reactions

    RECALL…Redox Reactions

    • Catabolic pathways yield energy

      • Due to the transfer of electrons

    • Redox reactions

      • Transfer e-’s from one reactant to another by oxidation and reduction

        • In oxidation

          • Substance loses e-s (it’s oxidized)

        • In reduction

          • Substance receives e-s (it’s reduced)


    Examples of redox reactions

    becomes oxidized(loses electron)

    Na + Cl Na+ + Cl–

    becomes reduced(gains electron)

    Examples of redox reactions

    Xe- + Y  X + Ye-

    **energy must be added to remove e-

    X = e- donor = reducing agentand reduces Y.

    Y = e- recipient = oxidizing agentand oxidizes X.


    Oxidation of organic fuel molecules during cellular respiration

    becomes oxidized

    C6H12O6 + 6O2 6CO2 + 6H2O + Energy

    becomes reduced

    Oxidation of Organic Fuel Molecules During Cellular Respiration

    • During cellular respiration

      • Glucose is oxidized

      • oxygenis reduced

      • E-’s lose potential energy  energy is released

    http://student.ccbcmd.edu/~gkaiser/biotutorials/cellresp/ets_flash.html


    Ap biology ms gaynor

    2 e– + 2 H+

    2 e– + H+

    NAD+

    NADH

    H

    Dehydrogenase

    O

    O

    H

    H

    Reduction of NAD+

    +

    +

    2[H]

    C

    NH2

    NH2

    C

    (from food)

    Oxidation of NADH

    N

    N+

    Nicotinamide(reduced form)

    Nicotinamide(oxidized form)

    CH2

    O

    O

    O

    O–

    P

    O

    H

    H

    OH

    O

    O–

    HO

    P

    NH2

    HO

    CH2

    O

    N

    N

    H

    N

    H

    N

    O

    H

    H

    HO

    OH

    Figure 9.4

    Electrons are not transferred directly to oxygen but are passed first to a coenzyme called NAD+ or FAD

    NAD+ and FAD= e- acceptor and oxidating agent


    Ap biology ms gaynor

    2 H

    +

    1/2 O2

    (from food via NADH)

    Controlled release of energy for synthesis ofATP

    2 H+ + 2 e–

    ATP

    ATP

    Free energy, G

    Electron transport chain

    ATP

    2 e–

    1/2 O2

    2 H+

    H2O

    Electron Flow =

    (b) Cellular respiration

    food  NADH/FADH2 ETC  oxygen


    The stages of cellular respiration

    The Stages of Cellular Respiration

    • Respiration is a cumulative process of 3 metabolic stages

      1. Glycolysis

      2. The citric acid cycle

      3. Oxidative phosphorylation


    The 3 stages

    The 3 Stages

    • Glycolysis

      • Breaks down glucose into 2 molecules of pyruvate

      • Makes NADH

    • Kreb’s Cycle (Citric acid cycle)

      • Completes the breakdown of glucose

      • Makes NADH and FADH2

    • Oxidative phosphorylation

      • Driven by the electron transport chain

      • Generates ATP


    Ap biology ms gaynor

    Electrons carried

    via NADH and

    FADH2

    Electrons

    carried

    via NADH

    Oxidativephosphorylation:electron transport andchemiosmosis

    Citric acid cycle

    Glycolsis

    2 Pyruvate

    Glucose

    Cytoplasm

    Mitochondrion Matrix

    ATP

    ATP

    ATP

    Substrate-level

    phosphorylation

    Oxidative

    phosphorylation

    Substrate-level

    phosphorylation

    Figure 9.6

    • An overview of cellular respiration

    Inner Mitochondrion Membrane (Cristae)


    Ap biology ms gaynor

    Enzyme

    Enzyme

    ADP

    P

    Substrate

    +

    ATP

    Product

    Figure 9.7

    • Both glycolysis and the citric acid cycle

      • Can generate ATP by substrate-level phosphorylation (not using ATP synthase!)


    Stage 1 glycolysis

    Stage #1: Glycolysis

    • Glycolysis produces energy by oxidizing glucose  pyruvate

    • Glycolysis

      • Means “splitting of sugar”

      • Breaks down glucose into pyruvate

      • Occurs in the cytoplasmof the cell

        1 glucose breaks down  4 ATP made + 2 pyruvate molecules

        (net gain of 2 ATP…NOT 4 ATP)


    Ap biology ms gaynor

    Glycolysis

    Oxidativephosphorylation

    Citricacidcycle

    ATP

    ATP

    ATP

    Energy investment phase

    1 Glucose

    2 ADP + 2

    used

    P

    2 ATP

    Energy payoff phase

    formed

    4 ATP

    4 ADP + 4

    P

    2 NAD+ + 4 e- + 4 H +

    2 NADH

    + 2 H+

    2 Pyruvate + 2 H2O

    Glucose

    2 Pyruvate + 2 H2O

    4 ATP formed – 2 ATP used

    2 ATP

    + 2 H+

    2 NADH

    2 NAD+ + 4 e– + 4 H +

    • Glycolysis consists of two major phases

      1. Energy investment phase (endergonic= uses 2 ATP)

      2. Energy payoff phase

      (exogonic = makes 4 ATP)


    Glycolysis

    Glycolysis

    NET

    • Glucose  2 pyruvate (pyruvic acid) + 2 H2O

    • 4 ATP formed – 2 ATP used  2 ATP GAIN

      • substrate-level phosphorylation used

    • 2 NAD+ + 4e- + 4H+  2 NADH + 2H+

      **Glycolysis can proceed WITHOUT O2


    The energy investment payoff phases of glycolysis

    The energy investment & Payoff phases of Glycolysis

    • Let’s take a closer look….

      • Page 166-167 in textbook

      • 10 steps in glycolysis occuring in 2 phases


    Ap biology ms gaynor

    CH2OH

    Citric

    acid

    cycle

    H

    H

    Oxidative

    phosphorylation

    H

    Glycolysis

    H

    HO

    HO

    OH

    H

    OH

    Glucose

    1

    2

    3

    5

    4

    ATP

    Hexokinase

    ADP

    CH2OH

    P

    O

    H

    H

    H

    H

    OH

    HO

    H

    OH

    Glucose-6-phosphate

    Phosphoglucoisomerase

    CH2O

    P

    O

    CH2OH

    H

    HO

    HO

    H

    H

    HO

    Fructose-6-phosphate

    ATP

    Phosphofructokinase

    ADP

    CH2

    O

    O

    CH2

    P

    P

    O

    HO

    H

    OH

    H

    HO

    Fructose-

    1, 6-bisphosphate

    Aldolase

    H

    O

    CH2

    P

    Isomerase

    C

    O

    O

    C

    CHOH

    CH2OH

    O

    CH2

    P

    Dihydroxyacetone

    phosphate

    Glyceraldehyde-

    3-phosphate

    Figure 9.9 A

    Phase #1: The Investment Phase of Glycolysis(endergonic)


    Ap biology ms gaynor

    • Phase #2: The Payoff Phase of Glycolysis

      (exogonic)

    2 NAD+

    Triose phosphate

    dehydrogenase

    P i

    2

    2

    NADH

    + 2 H+

    10

    7

    9

    6

    8

    2

    O

    C

    O

    P

    CHOH

    P

    CH2

    O

    1, 3-Bisphosphoglycerate

    2 ADP

    Phosphoglycerokinase (PFK)

    2 ATP

    O–

    2

    C

    CHOH

    O

    P

    CH2

    3-Phosphoglycerate

    Phosphoglyceromutase

    O–

    2

    C

    O

    C

    P

    H

    O

    CH2OH

    2-Phosphoglycerate

    Enolase

    2 H2O

    O–

    2

    C

    O

    P

    C

    O

    CH2

    Phosphoenolpyruvate

    2 ADP

    Pyruvate kinase

    2 ATP

    O–

    2

    C

    O

    C

    O

    CH3

    Figure 9.8 B

    Pyruvate

    • Phosphofructoskinase (PFK)

    • is an allosteric enzyme

    • ATP acts as an allosteric inhibitor to PFK

    • High [ATP]  stops glycolysis via inhibition (blocks active site)


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    Glycolysis

    • http://www.northland.cc.mn.us/biology/Biology1111/animations/glycolysis.html

    • http://www.hippocampus.org/AP%20Biology%20II

      • Watch Glycolysis


    Stage 2 the kreb s cycle

    Stage #2: The Kreb’s Cycle

    • The citric acid cycle

      • Takes place in the matrix of the mitochondrion

        **NEEDS O2 TO PROCEED

        (unlike glycolysis)


    Ap biology ms gaynor

    CYTOSOL

    MITOCHONDRION

    NAD+

    + H+

    NADH

    O–

    CoA

    S

    2

    C

    O

    C

    O

    C

    O

    CH3

    1

    3

    Acetyle CoA

    CH3

    Coenzyme A

    (a vitamin)

    CO2

    Pyruvate

    Transport protein

    Figure 9.10

    • Stage #1 ½ : The Citric Acid Cycle

    • Before the citric acid cycle can begin

      • Pyruvate must first be converted to acetyl CoA, which links the citric acid cycle to glycolysis

    Acetyl group= unstable

    Uses active transport

    Diffuses out of cell


    The kreb s cycle

    The Kreb’s Cycle

    • Also called the “Tricarboxylic Acid Cycle”or the“Citric Acid cycle”

    • NAD+ and FAD (both are coenzymes) = electron “carriers”; proton acceptors

      • They are reduced and carry e-’s from Citric cycle to ETC

      • Dehydrogenase catalyzes hydrogen transfer reaction


    Nad and fad

    NAD+ and FAD

    Oxidized FormReduced Form

    NAD+ NADH (2 e-, 1 H)

    FAD FADH2(4 e-, 2 H)

    THINK: FADH2 come into play in the 2nd stage of cellular respiration; it is also the 2nd electron carrier 


    Ap biology ms gaynor

    Pyruvate (from glycolysis,2 molecules per glucose)

    Glycolysis

    Citricacidcycle

    Oxidativephosphorylation

    ATP

    ATP

    ATP

    CO2

    CoA

    NADH

    + 3 H+

    Acetyle CoA

    CoA

    CoA

    Citricacidcycle

    2 CO2

    3 NAD+

    FADH2

    FAD

    3 NADH

    + 3 H+

    ADP + P i

    ATP

    Figure 9.11

    An overview of the citric acid cycle

    (this occurs for EACH pyruvate molecule)


    The kreb s cycle1

    The Kreb’s Cycle

    • Let’s take a closer look….

      • Page 169 in textbook

      • 8 steps in citric cycle in MATRIX

      • 1 turn of cycle  2 reduced carbons enter  2 oxidized carbons leave


    Ap biology ms gaynor

    Citric

    acid

    cycle

    Oxidative

    phosphorylation

    Glycolysis

    S

    CoA

    C

    O

    CH3

    Acetyl CoA

    CoA

    SH

    O

    C

    COO–

    H2O

    NADH

    1

    COO–

    CH2

    + H+

    COO–

    CH2

    COO–

    NAD+

    Oxaloacetate

    C

    8

    COO–

    HO

    CH2

    2

    CH2

    HC

    COO–

    COO–

    COO–

    HO

    CH

    HO

    CH

    Malate

    Citrate

    COO–

    CH2

    Isocitrate

    COO–

    CO2

    Citric

    acid

    cycle

    3

    H2O

    7

    NAD+

    COO–

    NADH

    COO–

    CH

    + H+

    Fumarate

    CH2

    CoA

    SH

    HC

    a-Ketoglutarate

    CH2

    COO–

    C

    O

    4

    6

    SH

    CoA

    COO–

    COO–

    COO–

    CH2

    5

    CH2

    FADH2

    CO2

    CH2

    CH2

    NAD+

    FAD

    C

    O

    COO–

    Succinate

    NADH

    CoA

    P i

    S

    + H+

    Succinyl

    CoA

    GDP

    GTP

    ADP

    ATP

    Figure 9.12

    Figure 9.12


    Kreb s cycle summary

    Kreb’s Cycle Summary

    • pyruvate  Acetyl-CoA + 1 NADH

    • Each turn of cycle uses 1 pyruvate

      • So… 1 glucose molecule produces 2 turns of Kreb’s cycle

    • 1 turn of cycle yields 4 NADH, 1 ATP, and 1 FADH2 and 3 CO2 (as waste product)

      Remember to multiply by 2…why?

    • http://www.hippocampus.org/AP%20Biology%20II

      • Watch Pyruvate


    Stage 3 oxidative phosphorylation electron transport chain etc chemiosmosis

    Stage #3: Oxidative Phosphorylation(Electron Transport Chain (ETC) + Chemiosmosis)

    • Chemiosmosiscouples electron transport to ATP synthesis

    • NADH and FADH2

      • Donate e-s to ETC, which powers ATP synthesis using oxidative phosphorylation

        **OCUURS IN CRISTAE

        (folds of inner membrane)


    What is oxidative phosphorylation

    What is “oxidative phosphorylation”?

    • Recall…

      • Take H+/e-s away, molecule = “oxidized”

      • Give H+/e-s, molecule = “reduced”

      • Give phosphate, molecule = “phosphorylated”

    • So…oxidative phosphorylation = process that couples removal of H+’s/ e-’s from one molecule & giving phosphate molecules to another molecule


    The pathway of electron transport

    The Pathway of Electron Transport

    • In the ETC…

      • e-s from NADH and FADH2 lose energy in several steps

        **NEEDS O2 TO PROCEED

        (unlike glycolysis)


    Etc characteristics

    ETC Characteristics

    • Lots of proteins (cytochromes) in cristae  increases surface area

      • 1000’s (many) copies of ETC

    • ETC carries e-’s from NADH/FADH2 O2

    • O2 = pulls e-s “down” ETC due to electronegativity (high affinity for e-s)


    Ap biology ms gaynor

    http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120071/bio11.swf::Electron%20Transport%20System%20and%20ATP%20Synthesis

    Inner

    Mitochondrial

    membrane

    Oxidative

    phosphorylation.

    electron transport

    and chemiosmosis

    Glycolysis

    ATP

    ATP

    ATP

    H+

    H+

    H+

    H+

    Cyt c

    Protein complex

    of electron

    carriers

    Intermembrane

    space

    Q

    IV

    I

    III

    ATP

    synthase

    II

    Inner

    mitochondrial

    membrane

    H2O

    FADH2

    2 H+ + 1/2 O2

    FAD+

    NADH+

    NAD+

    ATP

    ADP +

    P i

    (Carrying electrons

    from, food)

    H+

    Mitochondrial

    matrix

    Chemiosmosis

    ATP synthesis powered by the flow

    Of H+ back across the membrane

    Electron transport chain

    Electron transport and pumping of protons (H+),

    which create an H+ gradient across the membrane

    Oxidativephosphorylation

    Figure 9.15

    Protin motive force is used!

    • Chemiosmosis and the electron transport chain


    Ap biology ms gaynor

    What happens at the end of the ETC chain?

    • At the end of the chain

      • Electrons are passed to oxygen, forming water

      • O2 = final e- acceptor

    • NAD delivers e- higher than FAD  NAD provides 50% more ATP


    Etc is a proton h pump

    ETC is a Proton (H+) Pump

    • Uses the energy from “falling” e-s (exergonic flow) to pump H+’s from matrix  to outer compartment

    • A H+ (proton) gradient forms inside mitochondria

    • ETC does NOT make ATP directly but provides stage for CHEMIOSOMOSIS to occur


    Recall chemiosmosis

    RECALL…Chemiosmosis

    • Is an energy-coupling mechanism that uses energy in the form of a H+ gradient across a membrane to drive cellular work

    • Uses ATP synthase

    • Makes ~90% of ATP in Cell Resp.

    • Proposed by Peter Mitchell (1961)


    Chemiosmosis the energy coupling mechanism

    A rotor within the membrane spins clockwise whenH+ flows past it down the H+ gradient.

    INTERMEMBRANE SPACE

    H+

    H+

    H+

    H+

    H+

    H+

    H+

    A protein anchoredin the membraneholds the knobstationary.

    A rod (or “stalk”)extending into the rotor/ knob alsospins, activatingcatalytic sites inthe knob.

    H+

    Three catalytic sites in the stationary knobjoin inorganic

    Phosphate to ADPto make ATP.

    ADP

    +

    ATP

    P i

    MITOCHONDRIAL MATRIX

    Figure 9.14

    Chemiosmosis: The Energy-Coupling Mechanism

    • ATP synthase

      • Is the enzyme that actually makes ATP

    http://www.sigmaaldrich.com/life-science/metabolomics/learning-center/metabolic-pathways/atp-synthase.html


    A comparison of chemiosmosis in chloroplasts and mitochondria

    A Comparison of Chemiosmosis in Chloroplasts and Mitochondria

    • Chloroplasts and mitochondria

      • Generate ATP by the SAME basic mechanism: chemiosmosis

      • But use different sources of energy to accomplish this

      • http://student.ccbcmd.edu/~gkaiser/biotutorials/cellresp/atpase_flash.html


    Ap biology ms gaynor

    • The spatial organization of chemiosmosis

      • Differs in chloroplasts and mitochondria

    • In both organelles

      • electron transport chains generate a H+ gradient across a membrane

    • ATP synthase

      • Uses this proton-motive force to make ATP


    Ap biology ms gaynor

    • At certain steps along the ETC

      • Electron transfer causes protein complexes to pump H+ from the mitochondrial matrix  intermembrane space

        • Inside (matrix) = low [H+]

        • Outside = high [H+]


    Ap biology ms gaynor

    • The resulting H+ gradient…

      • Stores energy

      • Drives chemiosmosis in ATP synthase

      • Is referred to as a proton-motive force


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    Electron shuttles

    span membrane

    MITOCHONDRION

    CYTOSOL

    2 NADH

    or

    2 FADH2

    2 FADH2

    2 NADH

    2 NADH

    6 NADH

    Glycolysis

    Oxidative

    phosphorylation:

    electron transport

    and

    chemiosmosis

    Citric

    acid

    cycle

    2

    Acetyl

    CoA

    2

    Pyruvate

    Glucose

    + 2 ATP

    + about 32 or 34 ATP

    by substrate-level

    phosphorylation

    by substrate-level

    phosphorylation

    by oxidative

    phosphorylation

    About

    36 or 38 ATP

    Maximum per

    glucose:

    Figure 9.16

    • There are three main processes in this metabolic enterprise

    + 2 ATP


    Ap biology ms gaynor

    • About 40% of the energy in a glucose molecule

      • Is transferred to ATP during cellular respiration, making ~36- 38 ATP


    Overall aerobic respiration

    Overall (Aerobic Respiration)

    ATP GRAND TOTAL = ~36-38 ATP per 1 GLUCOSE


    Ap biology ms gaynor1

    AP BiologyMs. Gaynor

    Chapter 9 (Part 2):

    Fermentation


    Fermentation

    Fermentation

    • Fermentation enables some cells to produce ATP without the use of oxygen (O2)

    • Cellular respiration

      • Relies on oxygen to produce ATP

    • In the absence of oxygen

      • Cells can still produce ATP through fermentation


    Ap biology ms gaynor

    • Glycolysis

      • Can produce ATP with or without oxygen, in aerobic or anaerobic conditions

      • Couples with fermentation to produce ATP


    Types of fermentation

    Types of Fermentation

    • Fermentation consists of

      • Glycolysis plus reactions that regenerate NAD+, which can be reused by glyocolysis


    Alcohol fermentation

    Alcohol Fermentation

    • Pyruvate is converted to ethanol (ethyl alcohol) in two steps, one of which releases CO2

      • Ex: bacteria and yeast


    Ap biology ms gaynor

    • In alcohol fermentation

      • Pyruvate is converted to ethanol (ethyl alcohol) in two steps, one of which releases CO2

        GLUCOSE  Pyruvate  Ethanol and CO2

        • Ex: bacteria and yeast do this


    Ap biology ms gaynor

    P1

    2 ATP

    2 ADP + 2

    O –

    C

    O

    C

    O

    Glucose

    Glycolysis

    CH3

    2 Pyruvate

    2 NADH

    2 NAD+

    CO2

    2

    H

    H

    H

    C

    C

    O

    OH

    CH3

    CH3

    2 Acetaldehyde (gets reduced by NADH. It is the oxidizing agent.)

    2 Ethanol

    (a) Alcohol fermentation

    2 ATP

    P1

    2 ADP + 2

    Glucose

    Glycolysis

    O–

    C

    O

    C

    O

    2 NADH

    2 NAD+

    CH3

    O

    C

    O

    H

    OH

    C

    CH3

    2 Lactate

    (b) Lactic acid fermentation


    Lactic acid fermentation

    Lactic Acid Fermentation

    • During lactic acid fermentation

      • Pyruvate is reduced directly to NADH to form lactate as a waste product

      • NO CO2 is released

        • Ex #1: fungus and bacteria in dairy industry to make cheese/ yogurt

        • Ex #2: Human muscle cells


    Ap biology ms gaynor

    P1

    2 ATP

    2 ADP + 2

    O –

    C

    O

    C

    O

    Glucose

    Glycolysis

    CH3

    2 Pyruvate

    2 NADH

    2 NAD+

    CO2

    2

    H

    H

    H

    C

    C

    O

    OH

    CH3

    CH3

    2 Acetaldehyde

    (gets reduced by NADH. It is the oxidizing agent.)

    2 Ethanol

    (a) Alcohol fermentation

    2 ATP

    P1

    2 ADP + 2

    Glucose

    Glycolysis

    O–

    C

    O

    C

    O

    2 NADH

    2 NAD+

    CH3

    O

    C

    O

    H

    OH

    C

    CH3

    2 Lactate

    (b) Lactic acid fermentation

    NO CO2made

    2 Pyruvate

    (gets reduced by NADH. It is the oxidizing agent.)


    Fermentation and cellular respiration compared

    Fermentation and Cellular Respiration Compared

    • Both fermentation and cellular respiration

      • Use glycolysis to oxidize glucose and other organic fuels to pyruvate


    Ap biology ms gaynor

    • Fermentation and cellular respiration

      • Differ in their final electron acceptor

        • Cell respriraition uses O2

        • Fermentation uses NAD+

    • Cellular respiration

      • Produces more ATP (~36-38 ATP)

    • Fermentation

      • Produces 2 ATP per cycle


    Ap biology ms gaynor

    Glucose

    CYTOSOL

    Pyruvate

    No O2

    present

    Fermentation

    O2 present

    Cellular respiration

    MITOCHONDRION

    Acetyl CoA

    Ethanol

    or

    lactate

    Citric

    acid

    cycle

    Figure 9.18

    • Pyruvate is a key juncture in catabolism


    The evolutionary significance of glycolysis

    The Evolutionary Significance of Glycolysis

    • Glycolysis

      • Occurs in nearly all organisms

      • Probably evolved in ancient prokaryotes before there was oxygen in the atmosphere

        • O2 in air ~2.7 bya; oldest prokaryotes ~3.5 bya

        • Also does not require organelles


    Ap biology ms gaynor

    Fats

    Proteins

    Carbohydrates

    Amino

    acids

    Fatty

    acids

    Sugars

    Glycerol

    Glycolysis

    Glucose

    Glyceraldehyde-3- P

    NH3

    Pyruvate

    Acetyl CoA

    Citric

    acid

    cycle

    Oxidative

    phosphorylation

    Figure 9.19

    • The catabolism of various molecules from food called “intermediates”


    Ap biology ms gaynor

    Glucose

    AMP

    Glycolysis

    Stimulates

    Fructose-6-phosphate

    +

    Phosphofructokinase

    Fructose-1,6-bisphosphate

    Inhibits

    Inhibits

    Pyruvate

    Citrate

    ATP

    Acetyl CoA

    Citric

    acid

    cycle

    Oxidative

    phosphorylation

    Figure 9.20

    • The control of cellular respiration through feedback inhibition

    • PFK is an allosteric enzyme


    Ap biology ms gaynor

    Excellent Overall Tutorial of Cell Respiration

    http://www.wiley.com/college/pratt/0471393878/student/animations/citric_acid_cycle/index.html


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