Understanding Cellular Respiration: Matter Recycling, Energy Production, and Pathways

1. Cellular Respiration

2. Matter is recycled Energy is not (Entropy) Cells use energy for work and growth Chemical products (CO2, H2O) are recycled

3. Catabolic Pathways and Production of ATP • The breakdown of organic molecules is exergonic • Two methods: • Cellular respiration • Fermentation

4. Catabolic Pathways and ATP • Cellular respiration • Aerobic • Most prevalent and efficient catabolic pathway • Consumes oxygen and organic molecules • Yields ATP – coupled reaction • Fermentation- partial degradation of sugars • Anaerobic

5. ATP and Cellular Work • Lots of energy in C-H bonds • Carbos are primary source of C-H, but lipids, proteins can be used

6. Steps of Respiration 1.Glycolysis 2. Kreb’s Citric Acid Cycle 3. Electron Transport Chain (ETC)

7. Cellular Respiration • What you need to know: • Where does each step take place? • What are the reactants and products?

8. Acetyl CoA

10. Glycolysis: ‘Split Sugar’ • In the cytosol • Anaerobic

11. 2 ATP are USED to initiate the reaction (activation energy) 4 ATP are FORMED near the end of glycolysis (coupled reaction)

12. Glucose is phosphorylated

14. Substrate-level phosphorylation

15. S-L phosphorylation

16. Products: (2) pyruvate 3C Pyruvic acid 4 ATP 2 NADH 2 H2O Glycolysis

17. Glycolysis • ATP used for work • NADH goes to ETC • H2O = metabolic water (?) • (2) Pyruvate go into mitochondria and formation of Acetyl CoA

18. Formation of Acetyl Coenzyme A • Transition between glycolysis (anaerobic) and Kreb’s (aerobic) • Pyruvate enters mitochondrion • CO2 removed - waste • NAD reduced to NADH (2x) • Goes to ETC • Acetyl Coenzyme A – goes to Kreb’s

19. Products 2 Acetyl CoA 2 NADH 2 CO2 Formation of Acetyl CoA

20. Krebs • Citric acid cycle • 2 turns of Krebs for each glucose to be oxidized • Takes place in the matrix - enzymes are in the mitochondrial matrix

21. Krebs • Exergonic • Energy used to produce NADH and FADH • 2 ATP produced • Oxaloacetate is regenerated

22. Products: 4 CO2 2 ATP 6 NADH 2 FADH2 Krebs

23. Krebs • H is ‘carried’ by NADH/FADH to ETC to generate ATP by OXIDATIVE PHOSPHORYLATION

24. Kreb’s ETC

25. ETC • Most ATP created during ETC by Oxidative phosphorylation • Energy from Krebs is stored in NADH and FADH2 • Flow of electronsdown the ETC generates 32 ATP

26. ETC • Carrier molecules (proteins) are embedded within the inner membrane • Each successive carrier has a higher electronegativity than the previous one • Electrons are ‘pulled’ downhill toOxygen • Strongest electronegativity

27. Proton gradient

28. Proton Gradient • H ions (protons) are ‘pumped’ across inner membrane by energy created whenelectrons are passed through the ETC • H+ ions build-up in the intermembrane space • H+ ions diffuse back across the membrane into the matrix through ATP synthase • Potential energy stored in H+ is used to make ATP

31. Summary of Aerobic Respiration

32. Summary: Glycolysis • Initial breakdown of glucose • 2 ATP invested • 4 ATP generated = net 2 • 2 NADH generated; electrons to ETC • 2 pyruvate molecules (C3)

33. Summary: Formation of Acetyl CoA • Aerobic • 2 Pyruvates into acetyl groups • Addition of coenzyme A • 2 NADH generated • 2 molecules of CO2 formed (waste)

34. Summary: Krebs • Aerobic • 2 ATP formed • 6 NADH • 2 FADH2 • 4 CO2 (waste) • First C compound formed – citric acid • Oxaloacetic acid regenerated

35. Summary:ETC • Aerobic • 32 – 34 ATP (40% effective) • Oxidative phosphorylation • H+ ions flow through inner membrane through ATP synthase to generate ATP • Proton-motive force

36. Anaerobic Respiration Fermentation

37. Pyruvate is the junction of catabolism

38. Alcohol Fermentation • Anaerobic • Pyruvate converted ethyl alcohol • Bacteria and yeasts

39. Lactic Acid Fermentation • Anaerobic • Pyruvate converted into lactate • Lactate carried to liver, converted back into pyruvate • Time

40. CATABOLISM OF OTHER FOODS