Oxidative Phosphorylation & Chemiosmosis Chapter 9.4

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

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

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

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

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

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 26-28 net ATP (depending on which e- carriers used) Final electron acceptor at the end of ETC is oxygen (O2 + 2e- + 2H+  H2O)

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

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)

ATP Yield Summary

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

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