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Cellular Respiration
Stage 4:
Electron Transport Chain
By Kim Foglia, Division Ave. H.S., Levittown, N.Y.
Modified by K. Crawford AP/IB Biology
2008-2009
Cellular respiration
By Kim Foglia, Divison Ave. H.S., Levittown, N.Y.
Modified by K. Crawford AP/IB Biology
What’s the
point?
The point
is to make
ATP!
ATP
By Kim Foglia, Division Ave. H.S., Levittown, N.Y.
Modified by K. Crawford AP/IB Biology
2008-2009
ATP accounting so far…
 Glycolysis  2 ATP
 Krebs cycle  2 ATP
 Life takes a lot of energy to run, need to
extract more energy than 4 ATP!
By Kim Foglia, Divison Ave. H.S., Levittown, N.Y.
Modified by K. Crawford AP/IB Biology
A working muscle recycles over
10 million ATPs per second
 II. Electron Transport Chain

Series of molecules built into inner
mitochondrial membrane
 Along cristae
 Consists of transport proteins & enzymes
Transport of electrons down ETC linked to
pumping of H+ to create H+ gradient
 Yields ~34 ATP from 1 glucose
 Only in presence of O2 (aerobic respiration)

By Kim Foglia, Divison Ave. H.S., Levittown, N.Y.
Modified by K. Crawford AP/IB Biology
O2
Electron Transport Chain
Inner
mitochondrial
membrane
Intermembrane space
C
Q
NADH
dehydrogenase
cytochrome
bc complex
Mitochondrial matrix
By Kim Foglia, Divison Ave. H.S., Levittown, N.Y.
Modified by K. Crawford AP/IB Biology
cytochrome c
oxidase complex
Remember the Electron Carriers?
Glycolysis
glucose
G3P
4 NADH
Time to
break open
the bank!
By Kim Foglia, Divison Ave. H.S., Levittown, N.Y.
Modified by K. Crawford AP/IB Biology
Oxidation of
pyruvate + Citric
acid cycle
8 NADH
2 FADH2
Electron Transport Chain
Builds a proton gradient!
NADH  NAD+ + H
e
p
intermembrane
space
H+
H+
H  e- + H+
H+
C
e–
Q
e–
NADH H
FADH2
NAD+
NADH
dehydrogenase
inner
mitochondrial
membrane
e–
H
FAD
2H+ +
cytochrome
bc complex
1
2
O2
H2O
cytochrome c
oxidase complex
mitochondrial
matrix
By Kim Foglia, Divison Ave. H.S., Levittown, N.Y.
What powers the proton (H+) pumps?…
Modified by K. Crawford AP/IB Biology
III. Stripping H from Electron Carriers
 NADH passes electrons 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)
Transport proteins in membrane pump H+
(protons) across inner membrane to
H
H
H H
intermembrane
space
H
H
H
H
H
+
+
+
+
+
+
H+
+
+
+
H+
C
e–
NADH
Q
e–
FADH2
FAD
NAD+
By Kim Foglia, Divison Ave. H.S., Levittown, NADH
N.Y.
Modified by K. Crawford AP/IB Biology
dehydrogenase
e–
2H+
cytochrome
bc complex
+
1
2
O2
H2O
cytochrome c
oxidase complex
ADP
+ Pi
ATP
H+
But what “pulls” the
electrons down the ETC?
O2
By Kim Foglia, Divison Ave. H.S., Levittown, N.Y.
Modified by K. Crawford AP/IB Biology
oxidative phosphorylation
Electrons flow downhill
 Electrons move in steps from
carrier to carrier downhill to O2
Each carrier more electronegative
 Controlled oxidation
 Controlled release of energy

By Kim Foglia, Divison Ave. H.S., Levittown, N.Y.
Modified by K. Crawford AP/IB Biology
“proton-motive” force
H+
H+
 Set up a H+


H+
gradient
Allow the protons
to flow through
ATP synthase
Synthesizes ATP
ADP + Pi  ATP
H+
H+
H+
H+
H+
ADP + Pi
ATP
By Kim Foglia, Divison Ave. H.S., Levittown, N.Y.
Modified by K. Crawford AP/IB Biology
H+
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
By Kim Foglia, Divison Ave. H.S., Levittown, N.Y.
Modified by K. Crawford AP/IB Biology
Chemiosmosis

By Kim Foglia, Divison Ave. H.S., Levittown, N.Y.
Modified by K. Crawford AP/IB Biology
1961 | 1978
Peter Mitchell
 Proposed chemiosmotic hypothesis

Revolutionary idea at the time
proton motive force
1920-1992
By Kim Foglia, Divison Ave. H.S., Levittown, N.Y.
Modified by K. Crawford AP/IB Biology
Pyruvate from
cytoplasm
Inner
+
mitochondrial H
membrane
H+
Intermembrane
space
Electron
transport
C system
Q
NADH
Acetyl-CoA
2. Electrons
provide energy
1. Electrons are harvested to pump protons
and carried to the transport
across the
system.
membrane.
-
NADH
Krebs
cycle
e-
e
FADH2
e-
ATP
e-
H2O
3. Oxygen joins
with protons to
form water.
1 O
2 +2
2H+
O2
H+
CO2
2
H+
32 ATP
4. Protons diffuse back in
down their concentration
By KimMitochondrial
Foglia, Divison Ave. H.S., Levittown,
N.Y. driving the
gradient,
matrix
Modified by K.
Crawford AP/IB Biologysynthesis of ATP.
H+
ATP
synthase
Pyruvate from
cytoplasm
Inner
+
mitochondrial H
membrane
H+
Intermembrane
space
Electron
transport
C system
Q
NADH
Acetyl-CoA
2. Electrons
provide energy
1. Electrons are harvested to pump protons
and carried to the transport
across the
system.
membrane.
-
NADH
Krebs
cycle
e-
e
FADH2
e-
ATP
e-
H2O
3. Oxygen joins
with protons to
form water.
1 O
2 +2
2H+
O2
H+
CO2
2
H+
32 ATP
4. Protons diffuse back in
down their concentration
By KimMitochondrial
Foglia, Divison Ave. H.S., Levittown,
N.Y. driving the
gradient,
matrix
Modified by K.
Crawford AP/IB Biologysynthesis of ATP.
H+
ATP
synthase
Cellular respiration
2 ATP
+ ~2 ATP + 2 ATP + ~34 ATP
By Kim Foglia, Divison Ave. H.S., Levittown, N.Y.
Modified by K. Crawford AP/IB Biology
Summary of cellular respiration
C6H12O6 + 6O2







 6CO2 + 6H2O + ~40 ATP
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?
By Kim Foglia, Divison Ave. H.S., Levittown, N.Y.
 Why do we breathe?
Modified by K. Crawford AP/IB Biology
Taking it beyond…
 What is the final electron acceptor in
H+
H+
H+
C
Electron Transport Chain?
e–
NADH
O2
Q
e–
FADH2
FAD
NAD+
NADH
dehydrogenase
e–
2H+ +
cytochrome
bc complex
1
2
O2
H2O
cytochrome c
oxidase complex
 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!
By Kim Foglia, Divison Ave. H.S., Levittown, N.Y.
Modified by K. Crawford AP/IB Biology
What’s the
point?
The point
is to make
ATP!
ATP
By Kim Foglia, Division Ave. H.S., Levittown, N.Y.
Modified by K. Crawford AP/IB Biology
2008-2009