1. Oxidative Phosphorylation & Chemiosmosis
Chapter 9.4

2. To Recap… Glycolysis produced: Prep Step produced:
2 ATP
2 pyruvate
2 NADH
Prep Step produced:
2 CO2
2 Acetyl CoA
Krebs Cycle produced:
4 CO2
2 FADH2
6 NADH

3. I can explain how oxidative phosphorylation couples electron transport to ATP synthesis.
Learning target 4

4. A few terms to know… Proton motive force Chemiosmosis
Potential energy of hydrogen gradient
Chemiosmosis
Generation of ATP from a proton gradient
Occurs in all living things
In the case of cellular respiration’s ETC, the proton in H+

5. Addition of a Pi to ADP happens 2 ways
Substrate level phosphorylation
Addition of phosphate group directly without a proton gradient and ATP Synthase
Enzyme-catalyzed reaction transfers Pi to ADP
Found in glycolysis and Krebs cycle
Oxidative phosphorylation
Using proton gradient created by ETC in cristae membrane to make ATP
ETC + Chemiosmosis = oxidative phosphorylation

6. 3. Electron Transport Chain
Stage that produces the most ATP
Attached to cristae/inner membrane
Uses energy from NADH and FADH2 to create a proton gradient and make ATP
Includes:
3 transmembrane proton pumps
Carrier molecules between pumps
Ubiquinone (Q)
Cytochromes (Cyt c) Q

7. 3. Electron Transport Chain
Each NADH drops its electrons at top of ETC (first proton pump)
Each e- hits all 3 proton pumps
Each e- makes 3 ATP
Each FADH2 drops its electrons at ubiquinone (Q)
e- skip 1st proton pump, so make less ATP
Each e- makes 2 ATP

8. 3. Electron Transport Chain
Electrons passed down ETC provide energy for pumping H+ ions from matrix into intermembrane space
Proton gradient powers ATP synthase to ADP + Pi  ATP as H+ diffuse back into matrix
1 glucose yields net ATP (depending on which e- carriers used)
Final electron acceptor at the end of ETC is oxygen
(O2 + 2e- + 2H+  H2O)

9. ETC Summary
All electron carrier molecules are oxidized (NAD+, FAD) and can be reused in glycolysis, prep step, and Krebs cycle
26 or 28 ATP produced
H2O

10. Accounting of ATP Production
40% of energy stored in glucose is transferred to ATP during cellular respiration
Remainder is lost as heat
Is this very efficient?
Maximum ATP produced is 38
Phosphorylation and redox reactions are not coupled, so ratio of NADH to ATP is not a whole number
Variation in efficiency of shuttle molecules (NAD+, FAD)
Proton motive force is not used solely to for ATP production (ex: also used to take in pyruvate from cytosol)

11. ATP Yield Summary

12. Other Fuel Molecules
Fats, proteins, and carbohydrates can be broken down to release energy
1g of fat  twice as much ATP as 1g of carbohydrate
Beta oxidation of fats
Breakdown of fatty acids into 2 carbon fragments that can enter the Krebs cycle as Acetyl CoA
Protein is broken into amino acids
Most used by cell to build protein
Excess amino acids converted into intermediates of glycolysis and Krebs and enters respiration that way
Carbohydrates broken down to monomers to fuel respiration

13. Cellular Respiration in Action
Glycolysis
Prep Step & Krebs Cycle
Electron Transport Chain