1. Cellular Respiration (continued)
Stage IV: Electron Transport Chain & Chemiosmosis

2. Recall... C6H12O6 + O2 6 CO2 + 6 H2O + 36 ATP
So far, in stages 1-3 (Glycolysis, Pyruvate Oxidation, and the Krebs Cycle) we have:
- broken down C6H12O6
- produced 6 CO2
- produced 4 (net) ATP
- produced 10 NADH
- produced 2 FADH2
These coenzymes will now go to Stage 4 to transfer energy to ATP

3. # ATP so far
2 from glycolysis 2 from Krebs Cycle 4 Total (All via substrate level phosphorylation)

4. Total # of Reduced Co-enzymes
2 NADH from glycolysis
2 NADH from pyruvate oxidation
6 NADH from Krebs cycle
10 NADH total
and 2 FADH2 from Kreb cycle

5. Stage and Location 1. Glycolysis: in the cytoplasm
2. Pyruvate Oxidation: in the mitochondrial matrix
3. Krebs Cycle: in the mitochondrial matrix
4. ETC & Chemiosmosis: within the inner mitochondrial membrane

7. Co-enzymes & Stage IV
All the reduced co-enzymes that have been produced will be used in the next stage of cellular respiration (the electron transport chain) which occurs in the mitochondrial matrix
However, the 2 NADHs made in glycolysis are in the cytoplasm

8. The 2 NADH made in glycolysis in the cytoplasm cannot enter the matrix
A “shuttle” will take its electrons and transfer it to a FAD to produce FADH2
This is the glycerol-phosphate shuttle

9. The Glycerol Phosphate Shuttles
The NADH is oxidized by the shuttle, turning into NAD+
NAD+ can be reused in glycolysis
The shuttle brings the electrons into the matrix
They reduce FAD into FADH2
So, there are actually 8 NADH and 4 FADH2 molecules available for Stage 4 (the ETC and Chemiosmosis)

10. Stage 4: Electron Transport Chain & Chemiosmosis
Occurs in the cristae (the folds of the inner mitochondrial membrane)
Folds allow for more surface area
NADH and FADH2 will transfer their hydrogen atom electrons

11. Electron Transport Chain (ETC)
A series of compounds (mostly proteins) within the inner mitochondrial membrane.
They are arranged in order of increasing electronegativity with the weakest at the beginning of the chain.
NADH cytochrome
Deyhydrogenase oxidase
WEAKEST ATTRACTOR STRONGEST ATTRACTOR
OF ELECTRONS OF ELECTRONS
Increasing eletronegativity

12. Protein complex
Coenzyme is oxidized
FADH2 transfers its electrons to Q – not NADH dehydrogenase

13. Through a series of redox reactions, 2 electrons from each NADH and FADH2 molecule get passed from compound to compound in the ETC chain always moving to the more electronegative compound
So each component is reduced, and then oxidized.
During the process energy is released (as the é move to more stable compounds)

14. Some of that energy is lost as heat
The rest of the energy is used to move protons (H+ ions) from the matrix to the intermembrane space.
The H+ move through proton pumps that are in the 3 membrane associated proteins
The last é acceptor is oxgyen (which is very electronegative ) from the matrix

15. Oxygen combines with the electrons and hydrogen ions to make water
½ (O2) + 2 é + 2 H H2O
From the matrix from the ETC from the matrix
Oxygen combines with the electrons and hydrogen ions to make water
(The reaction is catalyzed by the last protein complex – cytochrome oxidaze)

16. The electron transport process is highly exgergonic
Some of the energy was used to pump H+ into the intermembrane space
This energy is now stored in the electrochemical gradient of the inner mitochondrial membrane.
It will be used to synthesize ATP in CHEMIOSMOSIS

18. Chemiosmosis
During ETC, H+ accumulated in the intermitochondrial membrane
This creates an electronchemical gradient which creates a potential difference across the inner mito membrane
The energy stored in the gradient produces a proton-motive force (PMF)

19. The H+ can’t move back into the matrix on their own- they go through a proton channel called ATP synthase (also called ATPase)
As the H+ move through ATPase, the energy from the electrochemical gradient drives the synthesis or ATP from ADP and a free phosphate group
This is oxidative phosphorylation because the energy used to drive ATP synthesis came from the redox reactions of the ETC!

20. 10 NADH: 2 glycolysis 2 FADH2 = 4 ATP 2 pyruvate oxidation = 6 ATP
Each NADH will make 3 ATP
Each FADH2 will make 2 ATP
Remember... We made:
10 NADH: 2 glycolysis FADH2 = 4 ATP
2 pyruvate oxidation = 6 ATP
6 Krebs Cycle = 18 ATP
2 FADH2: Krebs = 4 ATP
Chemiosmosis Total: 32 ATP
2 ATP ATP ATP = 36 ATP
from glycolysis from Krebs from chemiosmosis

22. The continual production of ATP requires maintenance of H+ reservoir
H+ reservoir requires movement of é through ETC
ETC is dependent of having O2 as the final é acceptor

23. If there is no O2, then the ETC becomes “clogged” with é and H+ won’t be pumped into intermembrane space
Chemiosmosis will not occur and ATP won’t be made
NADH and FADH2 cannot oxidize
Therefore, only glycolysis would take place (because NADH and FADH2 needed for pyruvate oxidation and Krebs)

24. Animations
2010/student_view0/chapter7/animations_and _videos.html