1

Respiration: Occurs in two places in the cell

Cytoplasm and mitochondria

cytoplasm Matrix

Inner membrane

Outer membrane

Intermembrane space

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2

Respiration: Occurs in 3 stages

Glycolysis “split sugars”

6C sugar 2 ● 3C sugars

(glucose) (pyruvate)

Kreb’s cycle

3C sugar CO2 + NADH + FADH2

(pyruvate)

redox

Oxidative Phosphorylation

NAD+ & FADoxidized

NADH + FADH2

ATP madeADP + Pi

O2 is used (AEROBIC)

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3

Respiration: Occurs in 3 stages

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4

The RXNs of Respiration: Glycolysis

Glycolysis “split sugars”

6C sugar 2 ● 3C sugars

(glucose) (pyruvate)in cytoplasm

G3P

Glceraldehye-3-phosphateHigh energy phosphate from ATP

2 Phases

Energy investment phase:

Energy payoff phase:

NET:

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5

The RXNs of Respiration: Glycolysis

How is ATP made during Glycolysis?

Substrate level Phosphorylation

Transfer of phosphate from substrate directly to ADP

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6

The RXNs of Respiration: Glycolysis

Energy investment phase Energy payoff phase

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7

The RXNs of Respiration: Glycolysis

What do I need to know about glycolysis?

6C sugar 2 ● 3C sugars

(glucose) (pyruvate)

2 PhasesEnergy investment phaseEnergy payoff phase

Key step: G3P (intermediate) is oxidized to reduce NAD+ to NADH

ATP made by substrate level phosphorylationUsing kinases

Take place in cytoplasm

(will go to Kreb’s cycle in matrix of mitoch.)

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8

The RXNs of Respiration: Entering the Krebs cycle

Pyruvate in cytosol

Oxidized asit is transportedinto mitoch.

Acetyl CoA

72 protein transport complex1. Oxidation to release CO2

2. Reduction of NAD+ to NADH + H+

3. Coenzyme A linked to remaining 2 carbon sugar

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9

The RXNs of Respiration: Krebs cycle (citric acid cycle)

3Cpyruvate

NAD+NADH + H+

CO2

Acetyl-CoA

CoA

CoA

6CCitric acid

5C

4C

4CCO2

NADH + H+NAD+

NADH + H+

NAD+

ADPATP

substrate level phosphorylation

FAD

FADH2

NADH + H+

NAD+

Energy Totals for Krebs

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10

The RXNs of Respiration: Glycolysis and Krebs Energy totals

Key products of Glycolysis2 ATP2 NADH + H+

2 pyruvates (3C sugar)

Key products of Krebs2 ATP8 NADH + H+

2 FADH2

Need to do to make ATP?

Need to regenerate NAD+ and FAD

Oxidative Phosphorylation

1. Electron transport: oxidation of NADH and FADH2 to NAD + and FAD

2. Chemiosmosis will generate ATP

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11

The RXNs of Respiration: Electron Transport Chain

NADH + H+ + ½ 02 NAD+ + H20 ΔG << 0

Separate e-transport them thru several proteinsMultiple small rxns02 is ultimate acceptor of e-

multiple electron transport proteins involvedredox reactions – passed from 1 to the next

NADH enters at the beginning to donate its e-

FADH2 enters later (therefore FADH2 = 2/3 energy of NADH)

3 protein complexes pump e- from matrix into the intermembrane space

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The RXNs of Respiration:

Electron Transport Chain

NADH + H+ + ½ 02 NAD+ + H20

ΔG = -53 kcal

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13

The RXNs of Respiration: Electron Transport Chain

Chemiosmosis and the proton (H+) motive force

NAD+ + 2e- + 2 H+NADH + H+

As e- enters the electron transport chain H+ are pumped across the membrane (from matrix to intermembrane space)

H+ now in high concentration in the intermembrane space

H+ repel back into the matrix

Through the ATP synthase: channel which uses H+ gradient to make ATP

ATPADP + Pi

NADH 3 H+ complexes which generates – 3 ATPs madeFADH2 2 H+ complexes which generates – 2 ATPs made

Linking e- transport and H+ shuttling to ATP synthesis

FAD + 2e- + 2 H+FADH2

(2/3 energy of NADH –because enters ETC later!)

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The RXNs of Respiration: Electron Transport Chain

Show movie:http://vcell.ndsu.nodak.edu/animations/etc/movie.htm

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The RXNs of Respiration: ATP synthase

Energy is generated from ion gradientH+ ions: higher in the intermembrane space than in the matrix

ATPADP + Pi

Linking e- transport and H+ shuttling to ATP synthesis

Key is diffusion: spontaneous movement of a molecule from high conc. to low conc.

H+ repel back into the matrix

But membrane is impermeable to H+ ions – so can’t get across

___________ is the one channel H+ ions can get back acrosscaptures the energy of H+ movement down its conc. gradient to make ATP

H+ gradient +

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The RXNs of Respiration: ATP synthase

Show movie:http://vcell.ndsu.nodak.edu/animations/atpgradient/movie.htm

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The RXNs of Respiration: Energy totals

Krebs: matrix of mitochondria

2ATP + 8 NADH + 2FADH2

24 ATP 4 ATP

30 ATP totalsubstrate level phosphorylation

Glycolysis: cytosol

2ATP + 2 NADH

substrate level phosphorylation

(3 per NADH) (2 per FADH2)

4 ATP

6 ATPWhy 4 or 6 ATP?

NADH made by glycolysis in the cytoplasm is impermeable to membranes.Its e- are passed to either NAD+ or FAD in the Mitoch. via electron shuttling systems

NAD+

NADH + H+

e-

NADH +H+

NAD+FAD

FADH2

50:50chance

cytosol Mitoch. matrix

Pay a toll of 2 ATPs if passed to FAD

Grand Total36-38 ATPs

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18

Aerobic vs. Anaerobic Respiration

Aerobic requires O2:

Anaerobic does not requires O2:

Oxidative Phosphorylation

Need O2 to oxidize NADH and FADH2

(REDOX)

Fermentation: In anaerobic conditions –

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Normally:

19

Fermentation: In anaerobic conditions – make NAD+creak along on 2 ATPs per glucose

1Glucose (6C)

2 Pyruvate (3C)

2 NADH + H+

2 NAD+

2ATP

O2

36-38ATPsAnaerobic no O2

Muscle Yeast, bacteria

Lactic AcidRecovery NAD+

Get by on 2 ATPs per glucose!

EthanolRecovery NAD+

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20

Regulation of Respiration

No O2 turn on fermentation

Feedback control

Negative allosteric regulators

Positive allosteric regulator

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