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Oxidative Phosphorylation & Chemiosmosis. Chapter 9.4. To Recap…. Glycolysis produced: 2 ATP 2 pyruvate 2 NADH Prep Step produced: 2 CO 2 2 NADH 2 Acetyl CoA Krebs Cycle produced: 2 ATP 4 CO 2 2 FADH 2 6 NADH.
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Oxidative Phosphorylation & Chemiosmosis Chapter 9.4
To Recap… • Glycolysis produced: • 2 ATP • 2 pyruvate • 2 NADH • Prep Step produced: • 2 CO2 • 2 NADH • 2 Acetyl CoA • Krebs Cycle produced: • 2 ATP • 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 • 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 • 26or 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)
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
