Cellular Respiration: Stage 4
ELECTRON TRANSPORT AND
CHEMIOSMOSIS
Review: Stages of Cellular
Respiration
 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
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.
Components of the ETC
1) NADH dehydrogenase
2) Ubiquinone (Q) (Mobile Electron Carrier)
3) Cytochrome b-cl complex
4) Cytochrome c (Mobile Electron Carrier)
5) Cytochrome oxidase complex
NADH gives up its two electrons to
NADH dehydrogenase
 Q and cytochrome c
Shuttle electrons from one
carrier to another
 Electrons reach final
protein complex in the
chain
 Cytochrome Oxidase
Complex
 Contains the enzyme
cytochrome oxidase:
catalyzes the reaction
between the electrons,
protons, and molecular
oxygen to form _________.
Yeah...so?
 That’s great. We’ve used NADH to pump H+
ions into the intermembrane space.
 Where’s the ATP?
The Point of the ETC
 Highly exergonic: _____________________
 Electrons: NADH  oxygen. (∆ G) of -222
kJ/mol NADH.
 Free energy converted to electrochemical
potential energy:
 DUE TO THE PROTON GRADIENT FORMING
ACROSS THE INNER MITOCHONDRIAL
MEMBRANE.
Electrochemical Potential
Energy
 Type of energy stored by a battery
 Caused by accumulation of charged objects
(__________, __________, __________, etc.)
 The energy becomes stored in the
electrochemical gradient and will be used to
power ATP synthesis in the next part of the
process...
____________________________________
NADH vs. FADH2
 NADH passes electrons on to NADH
dehydrogenase
 Therefore, oxeach NADH molecule will help pump
________protons into the intermembrane space.
 FADH2 passes electrons on to Q.
 Help pump _________ protons.
NADH vs. FADH2
 NADH passes electrons on to NADH
dehydrogenase
 Therefore, oxidation of each NADH molecule will
help pump ________protons into the
intermembrane space.
 RESULT: three ATP/coenzyme
 FADH2 passes electrons on to Q.
 Oxidation of FADH2 will help pump _________
protons.
 RESULT: two ATP/coenzyme
Cytosolic NADH and Pyruvate
Oxidation/Krebs 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 to produce FADH2.
 FADH2 transfers electrons to Q  ____ ATP.
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.
... 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.
 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 looses 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.
Energy of gradient is ____________, and that energy
is used to create ATP from _____ and ____.
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:
_______________________.
 Gas exchange in aerobic unicellular organisms?
 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.
Substrate-level vs.
Oxidative Phosphorylation
Substrate-level Phosphorylation
Occurs in Glycolysis
 2 ATP in step 7 and 2 ATP in step 10
 Oxidative Phosphorylation
 Occur in
 Pyruvate oxidation
 Krebs cycle
 Electron transport & Chemiosmosis
The Exergonic Flow of Electrons in
Aerobic Respiration
What’s happening to the ‘lost’ energy?
THE ENERGETICS OF OXIDATIVE
PHOSPHORYLATION (1)
 Water can be formed in a test tube by combining
hydrogen gas and oxygen gas.
 Explosive reaction: bonding electrons move
closer to a nucleus in water than in their reactant
molecules.
 But... Water is formed at the end of the ETC...
WHY DON’T WE BLOW UP!?
THE ENERGETICS OF OXIDATIVE
PHOSPHORYLATION (2)
 Electrons moving through the ETC occupying
more _______________ configurations as they
move to ever more ___________ components.
 Energy is ______________ at each step.
 Therefore, electrons in a very ____________
state at the end of the ETC. Electrons gain more
_____________ when captured by oxygen.
 Resulting formation of water is a low-energy
emitting process.
THE ENERGETICS OF OXIDATIVE
PHOSPHORYLATION (3)
ETC Videos
http://www.youtube.com/watch?v=_PgjsfY71AM
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?