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Cellular Respiration
Stage 4:
Electron Transport Chain
AP Biology
2006-2007
What’s the
point?
The point
is to make
ATP!
ATP
AP Biology
2006-2007
Cellular respiration
AP Biology
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!
There’s got to be a better way!
I need a lot
more ATP!
AP Biology
A working muscle recycles over
10 million ATPs per second
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)

AP Biology
That
sounds more
like it!
O2

Review the video for electron transport and answer the
following questions:

Electron Transport Video
1.
2.
3.
4.
5.
6.
Where do the electrons for the ETC come from?
Where is this process taking place?
How do the electrons get shuttled down the ETC? How
is electronegativity involved?
What molecule is the final acceptor of the electrons?
What is the byproduct that is generated during the ETC?
The ETC does not generate ATP. What is it’s purpose?
Mitochondria
 Double membrane
outer membrane
 inner membrane

 highly folded cristae
 enzymes & transport
proteins

intermembrane space
 fluid-filled space
between membranes
AP Biology
Oooooh!
Form fits
function!
Electron Transport Chain
Inner
mitochondrial
membrane
Intermembrane space
C
Q
NADH
dehydrogenase
cytochrome
bc complex
Mitochondrial matrix
AP Biology
cytochrome c
oxidase complex
Remember the Electron Carriers?
Glycolysis
glucose
Krebs cycle
G3P
2 NADH
Time to
break open
the piggybank!
AP Biology
8 NADH
2 FADH2
Electron Transport Chain
Building proton gradient!
NADH  NAD+ + H
intermembrane
space
e
p
H+
H+
H  e- + H+
C
e–
NADH H
FADH2
NAD+
NADH
dehydrogenase
inner
mitochondrial
membrane
e–
Q
AP Biology
H+
e–
H
FAD
2H+ +
cytochrome
bc complex
1
2
O2
H2O
cytochrome c
oxidase complex
mitochondrial
matrix
Why does FADH2 drop its electrons on a different initial carrier?
What powers the proton (H+) pumps?…
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 electrons
do the work!
+
H
H+
H+
+
H+ H+ H
+
H+ H H+
C
e–
NADH
AP Biology
+
H
H+
Q
e–
FADH2
FAD
NAD+
NADH
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?
H 2O
O2
AP Biology
electrons
flow downhill
to O2
oxidative phosphorylation
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 ATP
instead of
fire!
AP Biology
“proton-motive” force
We did it!
 Set up a H+


H+
H+
H+
gradient
Allow the protons
to flow through
ATP synthase
Synthesizes ATP
ADP + Pi  ATP
Are we
there yet?
AP Biology
H+
H+
H+
H+
H+
ADP + Pi
ATP
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
So that’s
the point!
AP Biology
Chemiosmotic Model
 ATP Synthase video
AP Biology
1961 | 1978
Peter Mitchell
 Proposed chemiosmotic hypothesis

revolutionary idea at the time
proton motive force
1920-1992
AP Biology
Pyruvate from
cytoplasm
Inner
+
mitochondrial H
membrane
H+
Intermembrane
space
Electron
transport
C system
Q
NADH
Acetyl-CoA
1. Electrons are harvested
and carried to the
transport system.
NADH
Krebs
cycle
e-
e-
FADH2
e-
2. Electrons
provide energy
to pump
protons across
the membrane.
e-
H2O
3. Oxygen joins
with protons to
form water.
1 O
2 +2
2H+
O2
H+
CO2
ATP
Mitochondrial
matrix
AP Biology
H+
ATP
ATP
4. Protons diffuse back in
down their concentration
gradient, driving the
synthesis of ATP.
H+
ATP
synthase
ATP production
 Phosphorylation

Addition of phosphate group to an
organic molecule
 Substrate level phophorylation

Phosphate is added as a result of
enzymatic reaction
 Oxidative phosphorylation
AP Biology
GLUCOSE
AP Biology
ATP produced
GLUCOSE
2 ATP
2 ATP
produced directly
GLYCOLYSIS
AP Biology
GLUCOSE
16
14
38
ATP
2 ATP
8
34
2 ATP
produced directly
GLYCOLYSIS
+
2 NADH
+
6 ATP
through electron transport
PYRUVIC ACID
2 NADH
+
2 ATP
produced directly
ACETYL CoA
+
6 NADH
18 ATP
through electron transport
+
KREBS CYCLE
AP Biology
6 ATP
through electron transport
2 FADH2
4 ATP
through electron transport
Learning Check
 Which molecules are being oxidized and
reduced in each step of cell resp
(Hint think about your starting materials, end products, and
where the e-/H ions are going)
 Glycolysis?
 Krebs?
 ETC?
 Overall? (write the formula for cell resp)
AP Biology
January 9, 2012
 BellRinger

Previous Slide
 Objective
Develop a visual model to review the
important steps of cellular respiration
 Explore ways to determine the rate of cellular
resp in living organisms

 Homework
Cell Respiration Prelab
 Grade your own Break FR- due Wed

AP Biology
Video of Cellular Respiration
2 ATP
AP Biology
+
2 ATP
+
~36 ATP
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?
 Why do we breathe?
AP Biology
Other Nutrients
 Humans gain more
energy from
oxidation of fatty
acids than glucose

Lipids contain 9
kcal per gram

Lipids are broken
down and glycerol
enters glycolysis;
fatty acids are
converted to acetyl
CoA and enter the
citric acid cycle
AP Biology
Other Nutrients
 Proteins are
broken down into
amino acids
Amino acids are
deaminated (the
amino acids are
removed)
 The remaining
carbon chain
enters at various
points
 Proteins contain
about 4 kcal per
gram

AP Biology
Challenge
 Create a visual model that explains all three steps of
cellular respiration.
 You can draw it or act it out
 Keep track of what happens to:





The carbon molecules that start off in glucose
The reduction of oxygen
The electrons that are transferred by the electron
carriers
The hydrogen ions that create the chemiosmotic
gradient
The production of ATP
AP Biology
What’s the
point?
The point
is to make
ATP!
ATP
AP Biology
2006-2007
Testing it out
 What variables would effect the rate at
which respiration occurs?
 How might you set up an experiment to
test this?
 What could you do to measure the rate
of repspiration?
AP Biology