1. BI 211 Principles of Biology Fall 2009

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 Cellular Respiration: (Exergonic)
• 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. 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?
• glucose NADH ETC O2 (H2O)

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) 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 Step of Respiration Inputs Outputs CO2/H2O ATP produced
e- carriers loaded
Glycolysis
1 glucose
2 pyruvate
2H2O
2 net
2 NADH
Coenzyme Junction
Citric Acid Cycle
Electron Transport Chain
Oxidative phosphorylation
Fermentation

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 substrate to 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
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 Step of Respiration Inputs Outputs CO2/H2O ATP produced
e- carriers loaded
Glycolysis
1 glucose
2 pyruvate
2H2O
2 net
2 NADH
Coenzyme Junction
Citric Acid Cycle
Electron Transport Chain
Oxidative phosphorylation
Fermentation

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)
Location
Inputs/outputs
4. Catabolism of other biomolecules (Ch. 7)
Proteins
Fats