1. Chapter 9 • Cellular Respiration

2. Living cells • Require transfusions of energy from outside sources to perform their many tasks

3. Figure 9.1 • The giant panda obtains energy for its cells by eating plants

4. Light energy ECOSYSTEM Photosynthesisin chloroplasts Organicmolecules CO2 + H2O + O2 Cellular respirationin mitochondria ATP powers most cellular work Heatenergy Figure 9.2 • Energy flows into ecosystem as sunlight, leaves as heat

5. Catabolic pathways yield E by oxidizing organic fuels

6. Catabolic Pathways and Production of ATP • Breakdown of organic molecules is exergonic

7. Cellular respiration • Most prevalent and efficient catabolic pathway • Consumes O2 and organic molecules e.g. glucose • Yields ATP

8. To keep working cells regenerate ATP

9. Redox Reactions: Oxidation and Reduction • Catabolic pathways yield energy • Due to the transfer of electrons (e-)

10. Oxidation • Lose e- (oxidized) • Reduction • Gain e-, (reduced)

11. becomes oxidized(loses electron) Na + Cl Na+ + Cl– becomes reduced(gains electron) • Example of redox reaction

12. Oxidation of Organic Fuel Molecules During Cellular Respiration • Glucose is oxidized and oxygen is reduced

13. Stepwise Energy Harvest • Glucose oxidized in a series of steps

14. 2 e– + 2 H+ 2 e– + H+ NAD+ NADH H Dehydrogenase O O H H Reduction of NAD+ + + 2[H] C NH2 NH2 C (from food) Oxidation of NADH N N+ Nicotinamide(reduced form) Nicotinamide(oxidized form) CH2 O O O O– P O H H OH O O– HO P NH2 HO CH2 O N N H N H N O H H HO OH Figure 9.4 • Electrons f/ organic compounds • Usually first transferred to NAD+, a coenzyme

15. NADH (reduced form of NAD+) • Passes electrons to the e- transport chain

16. H2 + 1/2 O2 Explosiverelease ofheat and lightenergy (a) Uncontrolled reaction Free energy, G H2O Figure 9.5 A • Non stepwise e- transfer • Lg. release of E

17. e- transport chain • Passes e- in a series of steps instead of explosive reaction • Uses E from the e- transfer to form ATP

18. 2 H + 1/2 O2 (from food via NADH) Controlled release of energy for synthesis ofATP 2 H+ + 2 e– ATP ATP Free energy, G Electron transport chain ATP 2 e– 1/2 O2 2 H+ H2O Figure 9.5 B (b) Cellular respiration

19. The 3 Stages of Cellular Respiration • Glycolysis • Citric acid cycle (Kreb’s cycle) • Oxidative phosphorylation

20. Glycolysis • Breaks down glucose into two molecules of pyruvate • Citric acid (Kreb’s)cycle • Completes breakdown of glucose

21. Oxidative phosphorylation • Driven by e- transport chain • Generates ATP

22. Glycolsis Glucose Pyruvate Mitochondrion ATP Substrate-level phosphorylation Overview of cellular respiration

23. Citric acid cycle Glycolsis Glucose Pyruvate Mitochondrion ATP ATP Substrate-level phosphorylation Substrate-level phosphorylation

24. Electrons carried via NADH Electrons carried via NADH and FADH2 Oxidativephosphorylation:electron transportandchemiosmosis Glycolsis Citric acid cycle Glucose Pyruvate Mitochondrion ATP ATP ATP Substrate-level phosphorylation Oxidative phosphorylation Substrate-level phosphorylation

25. Electrons carried via NADH and FADH2 Electrons carried via NADH Oxidativephosphorylation:electron transport andchemiosmosis Citric acid cycle Glycolsis Pyruvate Glucose Cytosol Mitochondrion ATP ATP ATP Substrate-level phosphorylation Oxidative phosphorylation Substrate-level phosphorylation Figure 9.6 • Overview of cellular respiration

26. Enzyme Enzyme ADP P Substrate + ATP Product Figure 9.7 • Glycolysis and citric acid cycle generate ATP by substrate-level phosphorylation

27. Glycolysis harvests E by oxidizing glucose to pyruvate • Glycolysis • Means “splitting sugar” • Glucose  pyruvate • Occurs in cytoplasm

28. Glycolysis Oxidativephosphorylation Citricacidcycle ATP ATP ATP Energy investment phase Glucose P 2 ATP + 2 used 2 ATP Energy payoff phase formed P 4 ATP 4 ADP + 4 2 NAD+ + 4 e- + 4 H + + 2 H+ 2 NADH 2 Pyruvate + 2 H2O Glucose 2 Pyruvate + 2 H2O 4 ATP formed – 2 ATP used 2 ATP + 2 H+ 2 NADH 2 NAD+ + 4 e– + 4 H + Figure 9.8 • 2 major phases • E investment phase • E payoff phase

29. E investment phase

30. CH2OH Citric acid cycle H H Oxidative phosphorylation H Glycolysis H HO HO OH H OH Glucose 1 2 3 5 4 ATP Hexokinase ADP CH2OH P O H H H H OH HO H OH Glucose-6-phosphate Phosphoglucoisomerase CH2O P O CH2OH H HO HO H H HO Fructose-6-phosphate ATP Phosphofructokinase ADP CH2 O O CH2 P P O HO H OH H HO Fructose- 1, 6-bisphosphate Aldolase H O CH2 P Isomerase C O O C CHOH CH2OH O CH2 P Dihydroxyacetone phosphate Glyceraldehyde- 3-phosphate Figure 9.9 A

31. E payoff phase

32. 2 NAD+ Triose phosphate dehydrogenase P i 2 2 NADH + 2 H+ 10 7 9 8 6 2 O C O P CHOH P CH2 O 1, 3-Bisphosphoglycerate 2 ADP Phosphoglycerokinase 2 ATP O– 2 C CHOH O P CH2 3-Phosphoglycerate Phosphoglyceromutase O– 2 C O P C H O CH2OH 2-Phosphoglycerate Enolase 2 H2O O– 2 C O P C O CH2 Phosphoenolpyruvate 2 ADP Pyruvate kinase 2 ATP O– 2 C O C O CH3 Figure 9.8 B Pyruvate

33. Citric acid (Kreb’s) cycle completes the E-yielding oxidation of organic molecules • Takes place in matrix of mitochondrion

34. CYTOSOL MITOCHONDRION + H+ NAD+ NADH O– CoA S 2 C O C O C O CH3 1 3 CH3 Acetyle CoA Pyruvate CO2 Coenzyme A Transport protein Figure 9.10 • Pyruvate first converted to acetyl CoA, links cycle to glycolysis

35. Pyruvate(from glycolysis,2 molecules per glucose) Oxidativephosphorylation Glycolysis Citricacidcycle ATP ATP ATP CO2 CoA NADH + 3 H+ Acetyle CoA CoA CoA Citricacidcycle 2 CO2 FADH2 3 NAD+ 3 NADH FAD + 3 H+ ADP + Pi ATP Figure 9.11 • Overview of citric acid cycle

36. Closer look at citric acid cycle

37. Citric acid cycle Oxidative phosphorylation Glycolysis S CoA C O CH3 Acetyl CoA CoA SH H2O O C COO– NADH 1 COO– CH2 + H+ COO– CH2 COO– NAD+ Oxaloacetate 8 C COO– HO CH2 2 CH2 HC COO– COO– COO– HO CH HO CH Malate Citrate COO– CH2 Isocitrate COO– CO2 Citric acid cycle 3 H2O 7 NAD+ COO– NADH COO– CH + H+ Fumarate CH2 CoA SH HC a-Ketoglutarate CH2 COO– C O 4 6 SH CoA COO– COO– COO– CH2 5 CH2 FADH2 CO2 CH2 CH2 NAD+ FAD C O COO– Succinate NADH CoA S P i + H+ Succinyl CoA GDP GTP ADP ATP Figure 9.12 Figure 9.12

38. Oxidative phosphorylation • Chemiosmosis couples e- transport to ATP synthesis • NADH and FADH2 • Donate e- to e- transport chain, which powers ATP synthesis via oxidative phosphorylation

39. Electron Transport Chain • e- from NADH and FADH2 lose E in steps

40. NADH 50 FADH2 Multiproteincomplexes I 40 FAD FMN II Fe•S Fe•S O III Cyt b 30 Fe•S Cyt c1 IV Cyt c Free energy (G) relative to O2 (kcl/mol) Cyt a Cyt a3 20 10 0 O2 2 H + + 12 Figure 9.13 H2O • At end of the chain e- passed to O2, forming water

41. A rotor within the membrane spins clockwise whenH+ flows past it down the H+ gradient. INTERMEMBRANE SPACE H+ H+ H+ H+ H+ H+ H+ A stator anchoredin the membraneholds the knobstationary. A rod (for “stalk”)extending into the knob alsospins, activatingcatalytic sites inthe knob. H+ Three catalytic sites in the stationary knobjoin inorganic Phosphate to ADPto make ATP. ADP + ATP P i MITOCHONDRIAL MATRIX Figure 9.14 Chemiosmosis: The Energy-Coupling Mechanism • ATP synthase • Enzyme that actually makes ATP

42. e- transfer pumps H+ f/ mitochondrial matrix to intermembrane space

43. Resulting H+ gradient • Stores E • Drives chemiosmosis • Referred to as a proton-motive force

44. Chemiosmosis • E-coupling mechanism, drives cellular work

45. Inner Mitochondrial membrane Oxidative phosphorylation. electron transport and chemiosmosis Glycolysis ATP ATP ATP H+ H+ H+ H+ Cyt c Protein complex of electron carners Intermembrane space Q IV I III ATP synthase Inner mitochondrial membrane II H2O FADH2 2 H+ + 1/2 O2 FAD+ NADH+ NAD+ ATP ADP + P i (Carrying electrons from, food) H+ Mitochondrial matrix Chemiosmosis ATP synthesis powered by the flow Of H+ back across the membrane Electron transport chain Electron transport and pumping of protons (H+), which create an H+ gradient across the membrane Figure 9.15 Oxidative phosphorylation • Chemiosmosis and the e- transport chain

46. An Accounting of ATP Production by Cellular Respiration • During respiration, most E flows: • Glucose  NADH  electron transport chain  proton-motive force  ATP

47. Electron shuttles span membrane MITOCHONDRION CYTOSOL 2 NADH or 2 FADH2 2 FADH2 2 NADH 2 NADH 6 NADH Glycolysis Oxidative phosphorylation: electron transport and chemiosmosis Citric acid cycle 2 Acetyl CoA 2 Pyruvate Glucose + 2 ATP + 2 ATP + about 32 or 34 ATP by oxidative phosphorylation, depending on which shuttle transports electrons from NADH in cytosol by substrate-level phosphorylation by substrate-level phosphorylation About 36 or 38 ATP Maximum per glucose: Figure 9.16 • 3 main processes in metabolism

48. ~ 40% of E in a glucose molecule • Transferred to ATP during cellular respiration, making ~ 38 ATP

49. Fermentation; produces ATP w/o O2 • Cellular respiration • Relies on O2 to produce ATP • In the absence of O2 fermentation

50. Glycolysis • Produces ATP w/ or w/o oxygen, aerobic or anaerobic conditions • Couples w/ fermentation to produce ATP