Lecture 2 Outline (Ch. 7)

2. Lecture 2 Outline (Ch. 7) • I. Overview of Cellular Respiration • Redox Reactions • Steps of Respiration • IV. Cellular Respiration • A. Glycolysis • B. Coenzyme Junction • C. Citric Acid Cycle (aka Krebs/TCA cycle) • D. Electron Transport Chain (ETC) • E. Chemiosmosis • Anaerobic respiration • Respiration using other biomolecules

3. Cellular Respiration Overall purpose: • convert fuels to energy • animals AND plants • complementary to photosynthesis

4. Cellular Respiration: (Exergonic) Cellular Respiration • catabolizes sugars to CO2 • requires O2 • at mitochondrion

5. Redox Reactions • as part of chemical reaction, e- are transferred • e- transfer = basis of REDOX reactions (reduction) (oxidation)

6. Redox Reactions • follow the H, e- w/them

7. Redox Reactions Equation for respiration

8. Redox Reactions • transfer of e- to oxygen is stepwise

9. • glucose NADH ETC O2 (H2O) Redox Reactions • e- moved by NAD+ (niacin) • when “carrying” e- (& H+), NADH • gained e- (& H+), reduced Where do e- come from? • food (glucose) Where do e- go?

10. Steps of Respiration • Steps of respiration: 1. glycolysis Coenzyme Junction 2. Citric acid cycle 3. ETC 4. Chemiosmosis

11. Cellular Respiration • Stages of respiration: 1. Glycolysis – prep carbons

12. Cellular Respiration 1. Glycolysis • 1 glucose (6C) 2 pyruvate (3C) • key points: - inputs - ATP - NAD+/NADH - CO2 and H2O - outputs • eukaryotes AND prokaryotes

13. Cellular Respiration Glycolysis -inputs: -outputs: Where do they go?

14. Cellular Respiration Coenzyme Junction • 2 pyruvate (3C) 2 Acetyl CoA (2C) • pyruvate joins coenzyme A (vitamin B) • 2 C lost (as CO2) • 2 NAD+  NADH

15. Steps of Respiration • Stages of respiration: 2. Citric acid cycle e- transfer: redox

16. Cellular Respiration 2. Citric acid cycle • few ATP so far • mitochondrial matrix • 2 Acetyl CoA (2C) join oxaloacetate (4C) • 2 citrate (6C) converted several steps, 4C lost (CO2) • e- to carriers (NAD+, FAD)

17. Citric acid cycle -inputs: -outputs: Where do they go?

18. Self-Check

20. Steps of Respiration • Steps of respiration: 1. glycolysis - cytosol Coenzyme Junction 2. Citric acid cycle - mitochondrial matrix 3. ETC - inner mitochondrial membrane 4. Chemiosmosis - inner membrane to intermembrane space

21. Steps of Respiration • Stages of respiration: • ETC • Proton Motive Force

22. Substrate-level phosphorylation Phosphate group moved from substrateto ADP yields ATP

23. Cellular Respiration 3. Electron transport chain (ETC) • lots of energy harvested • released in stages • so far, 4 ATP – substrate P • many ATP – oxidative phosphorylation

24. Cellular Respiration – mitochondria revisited

25. Cellular Respiration Electron transport chain (ETC) • ETC  e- collection molecules • embedded on inner mitochondrial membrane • accept e- in turn • e- ultimately accepted by O2 (O2 reduced to H2O)

26. Electron transport chain (ETC) -inputs: per glucose, -outputs: Where do they go? H+ NAD+/FAD

27. Steps of Respiration • Stages of respiration: 4. Chemiosmosis ATP produced!

28. Cellular Respiration 4. Chemiosmosis • ATP synthase: inner mitochondrial membrane • energy input ATP – H+ gradient • chemiosmosis – ion gradient to do work

29. Cellular Respiration 4. Chemiosmosis • Four parts to ATP synthase: Rotor, Stator, Rod, Knob • H+ must enter matrix here • Generates 1 ATP per ~3.4 H+

30. Cellular Respiration Summary of respiration • Cells convert ~ 40% of energy in glucose to energy in ATP • Most fuel efficient cars convert only ~ 25% of gasoline energy

31. Cellular Respiration - anaerobic • no O2 – no oxidative phosphorylation • fermentation - extension of glycolysis • substrate-level phosphorylation only • need to regenerate e- carrier (NAD+)

32. Cellular Respiration - anaerobic

34. Cellular Respiration - anaerobic • Types of fermentation - 1. alcohol • pyruvate converted to acetaldehyde • acetaldehyde accepts e- • ethanol produced

35. Cellular Respiration - anaerobic • Types of fermentation - 2. Lactic acid • pyruvate accepts e- • lactate produced

36. Cellular Respiration - anaerobic • inputs/outputs • alcohol • pyruvate in • CO2 and EtOH out • brewing & baking • lactic acid • pyruvate in • lactate out • muscle fatigue

37. Cellular Respiration • pyruvate - junction • O2 present – citric acid cycle • O2 absent - fermentation

38. Self-Check • Comparison of aerobic vs. anaerobic respiration: Aerobic Anaerobic • ATP made by: • ATP per glucose: • initial e- acceptor: • final e- acceptor:

39. Cellular Respiration – other biomolecules • Glucose catabolism = one option Cycle can run in reverse! • Proteins: – amino group removed – a.a. enter Krebs Cycle

40. Cellular Respiration – fats • Fats: Glycerol in at glycolysis - becomes pyruvate Fatty acids at coenzyme junction - becomes Acetyl CoA 2 carbons at a time via β-oxidation A fatty acid chain of 16 C is energetically equivalent to how many glucose molecules?

41. Self-Check

42. Lecture 2 Summary • 1. Respiration Overview (Ch. 7) • Purpose • Redox reactions • Electron carriers & final electron acceptors • 2. Locations of respiration steps, inputs/outputs, purpose, description (Ch. 7) • Glycolysis • Coenzyme Junction • Citric Acid/Krebs Cycle • ETC & Oxidative Phosphorylation [chemiosmosis] • 3. Differences with anaerobic respiration (Ch. 7) • Purpose • Location • Inputs/outputs • 4. Catabolism of other biomolecules (Ch. 7) • Proteins • Fats