ELECTRON TRANSPORT AND
CHEMIOSMOSIS
Cellular Respiration: Stage 4
Review: Stages of Cellular
Respiration (per 1 Glucose)
 Glycolysis: occurs in cytosol.
 Glucose  2 Pyruvate
 2 ATP
 2 NADH
 Pyruvate Oxidation: occurs in matrix
 2 Pyruvate  2 acetyl-CoA
 2 NADH
 Krebs Cycle: occurs in matrix
 2 acetyl-CoA  2 oxaloacetate (cycle)
 6 NADH
 2 FADH2
 2 ATP
Stage 4: Electron Transport
and Chemiosmosis
 NADH and FADH2 eventually transfer their
hydrogen atom electrons to series of
compounds in the ETC.
 Components of the ETC arranged in order of
increasing electronegativity
 Weakest attractor of electrons at beginning of
chain
 Strongest at the end.
How it works...
 Each component is alternatively reduced and
oxidized
 Reduced: gains two electrons from component
before it in the chain
 Oxidized: by losing two electrons to component
after it in the chain.
 Like a baton being handed from runner to
runner in a relay race.
As Electrons shuttle through
the ETC...
 Going from less stable to more stable
 Therefore, energy is _____________.
 This energy is used to move H+ ions from
the matrix into intermembrane space.
 Three proton pumps do this
 NADH dehydrogenase
 Cytochrome b-c1 complex
 Cytochrome oxidase complex
At end of ETC...
 Electrons very stable, therefore, extremely
electronegative substance needed
 _______________ strips two electrons from the
final protein complex in the chain
 Two protons added from matrix to form water.
 Oxygen is the FINAL ELECTRON ACCEPTOR
in the ETC.
 Oxygen is very ___________________.
Components of the ETC
1) NADH dehydrogenase (Pump)
2) Ubiquinone (Q) (Mobile Electron Carrier)
3) Cytochrome b-cl complex (Pump)
4) Cytochrome c (Mobile Electron Carrier)
5) Cytochrome oxidase complex (Pump)
NADH gives up its two electrons to
NADH dehydrogenase.
As electrons move through protein,
they lose energy. This energy is
used to pump H+ from matrix 
intermembrane space.
 Q shuttles electrons to
Cytochrome b-c1 complex
 Electrons move through
C b-c1 complex. Again,
electrons _______ energy,
powering the protein to
pump H+ ions from the
_________ to the
______________ space.
 C shuttles electrons from C
b1-c complex to cytochrome
oxidase.
 Electrons reach final
protein complex in the
chain
 Cytochrome Oxidase
Complex
 Again, H+ is pumped into
the intermembrane space.
 Contains the enzyme
cytochrome oxidase:
catalyzes the reaction
between the electrons,
protons, and molecular
oxygen to form _________.
 Needed because Oxygen is
electronegative enough to
pull stabilized electrons
through protein.
Yeah...so?
 Electrons from NADH and FADH2
donated to electron transport.
 As electrons move through the
chain of proteins, they lose
energy.
 Energy from each 2e- used to
pump one H+ ion from matrix to
intermembrane space of
mitochondrion.
 So, H+ is being moved OUT of the
matrix. Results of this?
____________________________
Electrochemical Potential
Energy
 Type of energy stored by a battery
 Caused by accumulation of charged objects
 The energy becomes stored in the
electrochemical gradient and will be used to
power ATP synthesis in the next part of the
process...
____________________________________
EACH H+ in the intermembrane space eventually
produces ONE ATP.
NADH vs. FADH2
(Formed in the matrix)
 NADH passes electrons on to to NADH
dehydrogenase
 Therefore, oxidation of each NADH molecule will help
pump ________protons into the intermembrane space.
 EACH NADH WILL POWER THE FORMATION OF ____ ATP.
 FADH2 passes electrons on to Q.
 Therefore, oxidation of each FADH2 molecule will help
pump _______ protons.
 EACH FADH2 WILL POWER THE FORMATION OF ____ ATP.
Cytosolic NADH
 Cytosolic NADH is produced by ___________.
 May diffuse through outer membrane into
intermembrane space.
 Intermembrane is impermeable to
NADH
 Glycerol-phosphate shuttle: transfers
electrons from cytosolic NADH to FAD (within
matrix) to produce FADH2.
 FADH2 transfers electrons to Q  ____ ATP.
How many ATP will one cytosolic NADH eventually
produce? _______________
Yazeed Essa Guilty…
by Michael Small | March 5, 2010 at 02:29 pm
Yazeed Essa, an Ohio Doctor, Has Been
Found Guilty of Murdering His Wife with
Cyanide Poison
Yazeed Essa was convicted of murder on Friday,
March 5th. The Ohio doctor was found guilty of
lacing his wife's calcium pills with cyanide so that
he could be with his mistress.
Essa fled to Lebanon after his wife's death, but
gave up an extradition fight and returned to Ohio
to face trial.
Yazeed Essa Guilty: Doctor Murdered Wife with Cyanide |
NowPublic News Coverage
http://www.nowpublic.com/world/yazeed-essa-guilty-doctormurdered-wife-cyanide-2587107.html#ixzz1FGGtO1QF
Cyanide
 Cyanide inhibits cytochrome oxidase activity
 This prevents _____________ from acting as
the final electron acceptor
 Shuts down the ETC, H+ pumps, and
consequently, ATP production.
 Coma  death
 Not poisonous to all organisms!
 MIT-13 (anaerobic bacteria) live on cyanide. Used
in the same way as aerobes use oxygen.
Importance of Cristae
 Allows multiple copies of the ETC to be
located throughout inner membrane.
 Increased ______________________ for
reactions to occur.
... and finally...
CHEMIOSMOSIS and OXIDATIVE ATP
SYNTHESIS(but some terms first)
TERMINOLOGY
 Electrochemical Gradient: concentration
gradient created by pumping ions into a
space surrounded by a membrane that is
impermeable to ions.
 Proton-motive force (PMF): a force that
moves protons through an ATPase complex
on account of the electrochemical gradient of
proteins across a biological membrane.
ETC forms an Electrochemical
Gradient
 Electrochemical gradient formed by ETC
 Electrical component: higher positive charge in the
_________________ space than the ________.
 Chemical component: higher concentration of protons
in the ____________space than the _____________.
 Inner membrane impermeable to H+ ions.
 Intermembrane space becomes H+ reservoir.
 (H+ reservoir = proton reservoir)
 Potential difference (voltage) across inner
mitochondrial membrane.
Electrochemical Gradient
drives Chemiosomosis
 Chemiosmosis: energy that drives synthesis of
ATP comes from the “osmosis” of protons.
 ____ forced to diffuse through protein channels
associated with ATP synthase (ATPase).
 Electrochemical gradient loses potential energy
which is converted to chemical potential energy:
ATP!
 This energy drives the synthesis of ADP + Pi 
ATP
Electrochemical Gradient and
the Formation of ATP
Fate of ATP
 ATP molecules transported through both
mitochondrial _______________ by
____________ diffusion into the
____________ where they are used to drive
___________ processes such as movement,
active transport, and synthesis reactions.
Relationship between ETC and
Chemiosmosis? (review...)
 Electron transport chain obtains electrons from
hydrogen atoms from _________ and
____________ molecules.
 At each sequential step in the ETC, electrons
_________ energy by becoming more
_____________.
 Energy is harnessed by pumping _________ into
the _____ reservoir.
 ________________ gradient is formed, which
forces _______ to diffuse back into the
mitochondrial matrix via a __________ complex.
Conditions Necessary for ETC
and Chemiosmosis
This is a continuous process
 H+ reservoir must be maintained  requires ____________
movement of __________ through the ETC  dependant
on availability of ______________ to act as the final
electron acceptor.
 Hence, why we have lungs and fish have gills:
_______________________.
 Continuous source of electrons  electrons are transferred
via _______ and _______  coenzymes are formed during
the first ____ stages of cellular respiration  in the first
three stages of cellular respiration, __________ is
catabolized  need of glucose means a need of _________.
 Hence, why heterotrophs must continually ____ and
photoautotrophs must continually ___________________.
Importance of Oxygen (in
aerobes)
 No chemical is electronegative enough to
oxidize the last protein in the chain, except
for oxygen.
 If no oxygen  no substance to act as final
electon acceptor  last protein can not be
‘freed up,’  ETC shuts down  FADH2 and
NADH can no longer be oxidized  no NAD+
or FAD to recycle back into steps 1, 2 and 3.
Homework: look this diagram over and study it
until you understand the idea.
The Exergonic Flow of Electrons in
Aerobic Respiration
What’s happening to the ‘lost’ energy?
THE ENERGETICS OF OXIDATIVE
PHOSPHORYLATION
Overall – CELLULAR
RESPIRATION!
Seatwork/Homework
 Read page 109 – 110
 Make notes and a diagram on the theoretical coenzyme
and ATP yield. This is for YOU to study from!
Answer the following questions:
1) The theoretical yield of ATP is 36. Give two reasons why
the actual yield may differ from this.
2) What is the estimated number of ATP molecules formed
for each glucose molecule?
 Read the section on “Efficiency of Energy
Conversion...” Answer the following questions:
 1) How is the efficiency of aerobic respiration
calculated?
 2) How does the efficiency of aerobic respiration
differ from glycolysis?
Seatwork/Homework
Read the section “Metabolic Rate.” Make notes
and answer the following questions:
1) What is metabolic rate?
2) What is BMR? For humans, how much
energy does the BMR account for ?
3) What are some factors that effect the BMR?
4) What is a Benzinger calorimeter? Briefly,
how does it work?
(skip the calculation)
Seatwork/Homework
Read the section on “Controlling Aerobic
Respiration.” Answer the following
questions:
1) What is phosphofructokinase? How does it
regulate aerobic respiration? (in terms of
ADP, ATP, and citrate).
2) How do NADH levels regulate respiration?