1. Stage 4: Electron Transport Chain (ETC) and Chemiosmosis

2. Recall Glycolysis
DIGESTION

3. Which was followed by…

4. So, what do we have at this point?
A small amount of ATP (the useful energy for cell functions)

5. and... LOTS OF REDUCED CARRIERS: NADH and FADH2
the electrons are the “currency” with which the bulk of the energy is obtained

6. Now this “currency” (the electrons) need to be exchanged for the “currency” used by cells.....

7. So....how do we go from
ELECTRONS TO
ATP

8. Electron Transport Chain
A series of redox reactions moves electrons along the inner membrane of the mitochondria
Components are arranged in order of increasing EN

9. Label your diagram…use different colours!
The Players
Label your diagram…use different colours!

10. Electron Transport Chain
NADH gives up 2 e- to the first protein- complex (NADH dehydrogenase)
e- flow is very exergonic
This E is used to pump protons out of matrix and into intermembrane space

11. Electron Transport Chain
Oxygen is used to oxidize the last protein (Strips off the 2e- )
With 2 protons (H+) from the matrix, H2O is formed
Where does the oxygen come from?

12. But what about FADH2?
FADH2 and NADH do not transfer their e- in the same way
NADH passes e- to the first protein complex NADH dehydrogenase (pumps 3 p+)
FADH2 passes e- to Q (pumps 2 p+)

13. One more problem…the inner mitochondrial membrane is impermeable to NADH!
Solution?
A shuttle system is used to pass e- from cytosolic NADH (produced during glycolysis) to the matrix

14. 2 Types of Shuttles Glycerol-Phosphate Shuttle most common
Transfers e- from cytosolic NADH to FAD to produce FADH2
Aspartate Shuttle
Transfers e- to NAD+ forming NADH

15. Electron Transport Chain
[p+ ] builds up in intermembrane space
p+ are actually Hydrogen ions...so an electrical gradient also exists
the [gradient] and electrical gradient create the force needed to push the protons back into the matrix (called the Proton Motive Force or PMF)

16. How do the protons pass through the membrane?
BUT…
the membrane is (mostly) impermeable to ions
How do the protons pass through the membrane?

17. through facilitated diffusion through the centre of an ATP synthase complex

18. ELECTRON TRANSPORT

19. Chemiosmosis
As H+ moves into the matrix through ATP synthase, energy is released
The energy is used to phosphorylate ADP to form ATP (oxidative phosphorylation)
Newly formed ATP are transported to the cytoplasm by facilitated diffusion (where they will be used to drive endergonic processes)

21. Can we get energy from other food sources?