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Cellular Respiration Stage 4: Electron Transport Chain. Cellular respiration. What’s the point?. The point is to make ATP !. ATP. ATP accounting so far…. Glycolysis  2 ATP Kreb’s cycle  2 ATP Life takes a lot of energy to run, need to extract more energy than 4 ATP !.

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slide3

What’s thepoint?

The pointis to makeATP!

ATP

atp accounting so far
ATP accounting so far…
  • Glycolysis 2ATP
  • Kreb’s cycle 2ATP
  • Life takes a lot of energy to run, need to extract more energy than 4 ATP!

There’s got to be a better way!

I need a lotmore ATP!

A working muscle recycles over 10 million ATPs per second

there is a better way

O2

There is a better way!
  • Electron Transport Chain
    • series of proteins built into inner mitochondrial membrane
      • along cristae
      • transport proteins& enzymes
    • transport of electrons down ETC linked to pumping of H+ to create H+ gradient
    • yields ~36 ATP from 1 glucose!
    • only in presence of O2 (aerobic respiration)

Thatsounds morelike it!

mitochondria
Mitochondria
  • Double membrane
    • outer membrane
    • inner membrane
      • highly folded cristae
      • enzymes & transport proteins
    • intermembrane space
      • fluid-filled space between membranes

Oooooh!Form fits function!

electron transport chain

Innermitochondrialmembrane

Electron Transport Chain

Intermembrane space

C

Q

cytochromebc complex

cytochrome coxidase complex

NADH dehydrogenase

Mitochondrial matrix

remember the electron carriers
Remember the Electron Carriers?

glucose

Krebs cycle

Glycolysis

G3P

8 NADH

2 FADH2

2 NADH

Time tobreak openthe piggybank!

electron transport chain1

e

p

1

2

Electron Transport Chain

Building proton gradient!

NADH  NAD+ + H

intermembranespace

H+

H+

H+

innermitochondrialmembrane

H  e- + H+

C

e–

Q

e–

H

e–

FADH2

FAD

H

NADH

2H+ +

O2

H2O

NAD+

cytochromebc complex

cytochrome coxidase complex

NADH dehydrogenase

mitochondrialmatrix

What powers the proton (H+) pumps?…

stripping h from electron carriers

H+

H+

H+

H+

H+

H+

H+

H+

H+

H+

H+

H+

C

e–

Q

e–

1

2

e–

FADH2

FAD

NADH

2H+ +

O2

H2O

NAD+

cytochromebc complex

NADH dehydrogenase

cytochrome coxidase complex

Stripping H from Electron Carriers
  • Electron carriers pass electrons & H+ to ETC
    • H cleaved off NADH & FADH2
    • electrons stripped from H atoms  H+ (protons)
      • electrons passed from one electron carrier to next in mitochondrial membrane (ETC)
      • flowing electrons = energy to do work
    • transport proteins in membrane pump H+ (protons) across inner membrane to intermembrane space

H+

H+

H+

TA-DA!!

Moving electronsdo the work!

ADP+ Pi

ATP

slide11

H2O

O2

But what “pulls” the electrons down the ETC?

electronsflow downhill to O2

oxidative phosphorylation

electrons flow downhill
Electrons flow downhill
  • Electrons move in steps from carrier to carrier downhill to oxygen
    • each carrier more electronegative
    • controlled oxidation
    • controlled release of energy

make ATPinstead offire!

we did it

H+

H+

H+

H+

H+

H+

H+

H+

ADP + Pi

H+

“proton-motive” force

We did it!
  • Set up a H+ gradient
  • Allow the protonsto flow through ATP synthase
  • Synthesizes ATP

ADP + PiATP

ATP

Are wethere yet?

chemiosmosis
Chemiosmosis
  • The diffusion of ions across a membrane
    • build up of proton gradient just so H+ could flow through ATP synthase enzyme to build ATP

Chemiosmosis links the Electron Transport Chain to ATP synthesis

So that’sthe point!

peter mitchell

1961 | 1978

Peter Mitchell
  • Proposed chemiosmotic hypothesis
    • revolutionary idea at the time

proton motive force

1920-1992

slide16

Intermembrane

space

Pyruvate from

cytoplasm

Inner

mitochondrial

membrane

H+

H+

Electron

transport

system

C

Q

NADH

e-

H+

2. Electrons provide energy to pump protons across the membrane.

1. Electrons are harvested and carried to the transport system.

e-

Acetyl-CoA

NADH

e-

H2O

e-

Krebs

cycle

3. Oxygen joins with protons to form water.

1

FADH2

O2

2

O2

+

2H+

H+

CO2

ATP

H+

ATP

ATP

4. Protons diffuse back indown their concentrationgradient, driving the synthesis of ATP.

ATP

synthase

Mitochondrial

matrix

cellular respiration1

~40 ATP

Cellular respiration

+

+

2 ATP

2 ATP

~36 ATP

summary of cellular respiration

C6H12O6

+

6CO2

+

6H2O

+

~40 ATP

6O2

Summary of cellular respiration
  • Where did the glucose come from?
  • Where did the O2 come from?
  • Where did the CO2 come from?
  • Where did the CO2 go?
  • Where did the H2O come from?
  • Where did the ATP come from?
  • What else is produced that is not listed in this equation?
  • Why do we breathe?
taking it beyond

H+

H+

H+

C

e–

Q

e–

1

2

e–

FADH2

FAD

NADH

2H+ +

O2

H2O

NAD+

cytochromebc complex

NADH dehydrogenase

cytochrome coxidase complex

Taking it beyond…
  • What is the final electron acceptor in Electron Transport Chain?

O2

  • So what happens if O2 unavailable?
  • ETC backs up
    • nothing to pull electrons down chain
    • NADH & FADH2 can’t unload H
  • ATP production ceases
  • cells run out of energy
  • and you die!
slide20

What’s thepoint?

The pointis to makeATP!

ATP