1. STAGE 4: ELECTRON TRANSPORT and CHEMIOSMOSIS

2. Electron Transport Chain (ETC)
series of compounds, mainly proteins, which are associated with the inner mitochondrial membrane
arranged in order of increasing electronegativity:
NADH dehydrogenase < ubiquinone < cytochrome b-c1 complex < cytochrome c < cytochrome oxidase complex

3. Electron Transport Chain (ETC)
Textbook p. 105

4. Electron Transport Chain (ETC)
Each component is alternately a. reduced (gaining two electrons from the component before it in the chain) b. oxidized (losing two electrons to the component after it in the chain)

5. Electron Transport Chain (ETC)
Most of the energy produced during the Kreb’s cycle is held in energy carriers such as NADH and FADH2 that stay within the mitochondrial matrix.
They transfer their high energy electrons to proteins on the inner membrane of the mitochondrion.

6. Electron Transport Chain (ETC)
Physical Characteristics:
- inner mitochondrial membrane
separates the matrix from the
outer compartment
- large proteins embedded
in inner membrane
- these proteins are the electron
carriers in the electron
transport chain (ETC)
- electron carriers arrayed side by
side like the links in the chain
- 3 of the proteins are called ion pumps

7. Electron Transport Chain (ETC)
There are 9 quicks steps that occur in the electron transport chain:

8. Electron Transport Chain (ETC)
(1) NADH transfers two high
energy electrons to the first
electron carrier: an ion pump.
(2) NADH changes to NAD+.
(3) The carrier protein uses
energy from the electrons to
pump two H+ ions from the
matrix into the outer
compartment.

9. Electron Transport Chain (ETC)
(4) The electrons are then passed
to the next protein in the chain
and then on to the third electron
carrier.
(5) This third protein is also
an ion pump. It uses a bit
more of the electron’s energy to
pump two H+ ions through the
membrane.
(6) The electrons shift again to
the fourth protein then to the
fifth. This protein is a third ion pump.

10. Electron Transport Chain (ETC)
(7) Using energy from the
electrons, the protein pumps two
more H+ ions into the outer
compartment.
(8) The two electrons are now
much lower in energy. They
combine with two H+ ions and
an oxygen atom. Oxygen,
absorbed from air during
inhalation is the final electron
acceptor at the end of the electron transport chain (ETC)
(9) A molecule of water (H2O) is formed.

11. Electron Transport Chain (ETC)
PATHS:
- NADH gives up 2 electrons to
the first ETC complex: NADH
dehydrogenase.
- Q and cytochrome c (mobile
electron carriers) shuttle the
electrons from one protein to
the next until they reach the
final protein complex in the
chain: cytochrome oxidase complex
- the enzyme cytochrome oxidase complex catalyzes (speeds up) the
reaction between the electrons, protons and molecular oxygen to
form water

12. Electron Transport Process
highly exergonic (energy of the products is less than the energy of the reactants)
free energy lost by the electron pair during electron transport is used to pump 3 protons into the intermembrane space
converts one form of energy into another:
chemical potential energy of electron position 
electrochemical potential energy of a proton gradient
that forms across the inner mitochondrial membrane

13. Three main points Electrochemical potential energy
Important to distinguish between NADH and FADH2 in terms of their relationship with the electron transport system
A distinction must be made between the NADH molecules produced in glycolysis and those produced in the pyruvate oxidation& Krebs cycle.

14. Electrochemical Potential Energy
- Stored energy possessed by a charged battery - NADH -> oxygen, free energy (-222kJ/mol) - Stored and will be used to power ATP synthesis (chemiosmosis)

15. NADH and FADH2 in the electron transport system
- NADH passes its electrons on to the 1st protein complex (NADH dehydrogenase)
- FADH2 transfers its electrons to Q, the second component of the chain
- The free energy released by the oxidation of FADH2 is used to pump 2 protons into the intermembrane space, while NADH pumps 3

16. A distinction between the NADH molecules
- The NADH molecules produced in glycolysis and those produced in the pyruvate oxidation& Krebs cycle are different
- NADH(glycolysis) in the cytoplasm may diffuse through the outer mitochondrial membrane into the intermembrane space.

17. 2 Shuttle Systems
- Glycerol-phosphate shuttle -> transfers the electrons from cystolic NADH to FAD to produce FADH2 and 2 ATP molecules(chemiosmosis) - Aspartate shuttle -> transfers electrons to NAD+ instead of FAD, forming NADH, and then three ATP molecules

18. - The many folds of the inner membrane increase surface area & allow multiple copies of the ETC
- A limited number of NAD+ and FAD molecules -> recycled
- The resulting oxidized compounds pick up more hydrogen atoms in glycolysis, pyruvate oxidation, or the Krebs cycle

19. Chemiosmosis and Oxidative ATP Synthesis
Chemiosmosis: a process for synthesizing ATP using the energy of an electrochemical gradient and the ATP synthase enzyme

20. The protons that accumulate in the intermembrane space of the mitochondion during electron transport create an electrochemical gradient that stores free energy
Electrochemical gradient: a concentration gradient created by pumping ions into a space surrounded by a membrane that is impermeable to the ions.

21. The free energy stored in the electrochemical gradient produces a proton-motive force(PMF) that moves protons through an ATPase complex
The energy of the gradient is reduced as the protons pass through the ATPase complex back into the mitochondrial matrix

22. Proton-motive force(PMF): a force that moves protons through an ATPase complex on account of the free energy stored in the form of an electrochemical gradient of protons across a biological membrane
ATPase: a catalyst for the synthesis of ATP from ADP and inorganic phosphate in the matrix
Electron transport followed by chemiosmosis is the last stage of the oxidative phosphorylation process

23. What Happens When it stops?
No food(glucose) = no electrons
Heterotrophs must keep eating
Autotrophs must keep photosynthesizing

24. No O2 = no flow of electrons in ETC since O2 is final electron acceptor, freeing up the pathway
There’s no chemical in body Electronegative enough to oxidize last protein, O2 used to free protein

25. H+ not pumped and the concentration becomes even between matrix and intermembrane space
Chemiosomosis and ATP manufacturing stops

26. As for NADH and FADH2…
ETC clogged since O2 isn’t there to take away the final electron, holding up the entire production line
NADH and FADH2 can’t give up their electrons, and remain in their reduced form unable to oxidize H from other glucose

27. Dependancy
Pyruvate Oxidation, Kreb’s Cycle, ETC and chemiosmosis are linked and all depend on glycolysis for pyruvate
ETC and chemiosmosis BOTH depend on O2 and electrons to function, in this way they are coupled

28. Electron Transport Chain (ETC)
tqAB_Yc&feature=related