1. Cellular Respiration

2. Cellular Respiration = Glucose Oxidation

3. Redox Reactions

4. Coenzyme NAD+ is an electron carrier. NAD+ - oxidized
Coenzyme NAD+ is an electron carrier NAD+ - oxidized NADH + H+ - reduced

5. NADH -Nicotinamide adenine dinucleotide
Coenzyme found in all cells
Made of 2 nucleotides

7. Mitochondrial structure - label

8. Mitochondrial structure

9. Cellular Respiration overview
Process
Starting Molecule
End product
Location
Substrate level phosphorylation
Energy shuttled to oxidative phosphorylation
Glycolysis
1 glucose
2 pyruvate
Cytosol
2 ATP
2 NADH
(intermediate step)
2 Acetyl Co-A,
2 CO2
Matrix of mitochondria
None

10. Substrate level phosphorylation
Process
Starting Molecule
End product
Location
Substrate level phosphorylation
Energy shuttled to oxidative phosphorylation
Krebs cycle
2 acetyl-CoA
4 CO2
Matrix of mitochondria
2 ATP
6 NADH,
2 FADH2
Oxidative phosphorylation
Electrons (carried by electron carriers)
32-34 ATP
(theoretical)
Inner membrane of mitochondria

11. Totals entering oxidative phosphorylation:
4 ATP from substrate phosphorylation
10 NADH (2 from glycolysis)
2 FADH2

12. NADH from glycolysis  2 ATP (need 1 to shuttle NADH into mitochondria)
NADH  3 ATP
FADH2  2 ATP
This is theoretical yield
Total energy produced = 36 – 38 ATP molecules
- 2 in glycolysis, 2 in Krebs, 32-34* in Oxidative phosphorylation
* 34 for plants (don’t spend an ATP to get NADH into mitochondria), 32 for animals

13. Glycolysis Glyco – glucose Lysis - splitting or breaking Pg. 162-163
How is glucose split?

14. Glycolysis summary How many reactions are required?
What catalyzes each reaction?
How many ATP are produced?
How many net ATP are produced?
What is the initial reactant?
What are the final products?
Where does this occur in the cell?

15. Glycolysis

16. Glycolysis summary How many reactions are required? 10
What catalyzes each reaction? Specific enzyme
How many ATP are produced? 4
How many net ATP are produced? 2
What is the initial reactant? glucose
What are the final products? Pyruvate, 2 ATP, 2 NADH
Where does this occur in the cell? cytosol

17. Krebs cycle (aka citric acid cycle)
What is the starting molecules for the Krebs cycle?
What was the ending molecules of glycolysis?

19. Krebs cycle (aka citric acid cycle)
What is the starting molecules for the Krebs cycle? Acetyl CoA
What was the ending molecules of glycolysis?
pyruvate

20. Pyruvate to Acetyl CoA Intermediate step: pyruvate oxidation
How many reactions needed to convert pyruvate to acetyl CoA?
What is “lost” in the process?
What is “gained” in the process?
Where does this occur?

22. Pyruvate to Acetyl CoA Intermediate step: pyruvate oxidation
How many reactions needed to convert pyruvate to acetyl CoA? 3
What is “lost” in the process? CO2, electron to NAD+
What is “gained” in the process? NADH, Acetyl CoA
Where does this occur? As pyruvate enters mitochondrion, in the mitochondrial matrix

23. Krebs Cycle – 1st step In first step:
Oxaloacetate (4 C) + Acetyl-CoA (2 C) yields citrate (6 C)
Oxaloacetate gets regenerated through Krebs cycle
“-ate” – conjugate bases of the organic acids
Carboxyl groups – can donate protons
i.e. citrate is the conjugate base of citric acid

24. Krebs cycle – p. 165 How many reactions?
What catalyzes these reactions?
How many ATP produced?
How are the ATP produced?
Where does the rest of the energy harvested go?

25. Krebs Cycle

27. Krebs cycle How many reactions? 8
What catalyzes these reactions? Specific enzymes
How many ATP produced? 1 per cycle (2 total)
How are the ATP produced? Substrate phosphorylation
Where does the rest of the energy harvested go?
Electron carriers: 3 NADH, 1 FADH2 per cycle
(6 NADH, 2FADH2 total)

28. Krebs cycle How many turns of the cycle for 1 molecule glucose?
What are the initial reactants? Final products?
Where does this occur?

29. Krebs cycle
How many turns of the cycle for 1 molecule glucose? 2 – since glucose splits into 2 pyruvate
What are the initial reactants? Final products?
Initial: 2 Acetyl CoA, 6 NAD+, 2 FAD, 2 ADP
Final: 4 CO2, 6 NADH, 2FADH2, 2 ATP
Where does this occur? In the mitochondrial matrix

30. Substrate level phosphorylation

31. Substrate Level Phosphorylation
As each bond of glucose is broken, energy is released:
If enough energy released all at once, the energy is used to directly phosphorylate ADP to make ATP
(substrate level phosphorylation)

32. -- If amount of energy released is small, electrons
-- If amount of energy released is small, electrons are taken off as units of energy and handed to an electron shuttle, NADH
NADH gathers all the electrons and passes them off to the electron transport chain , so they can make ATP through oxidative phosphorylation

33. Oxidative Phosphorylation: Electron Transport Chain & Chemiosmosis
Electron Transport Chain – see diagram on handout
Where do the electrons for the electron transport chain come from?
Why are electrons transferred from carrier to carrier?
Why does FADH2 enter at a different point than NADH?

35. Electron Transport Chain/Oxidative Phosphorylation
Electron Transport Chain – see diagram on handout
Where do the electrons for the electron transport chain come from? From glycolysis, intermediate, krebs
Why are electrons transferred from carrier to carrier? Transferred to more electronegative carrier
Why does FADH2 enter at a different point than NADH? Has higher electronegativity

36. What atom is the final acceptor of the electron?
Why?
What does it form?
What is gained during this process?

37. What atom is the final acceptor of the electron? oxygen
Why? Most electronegative
What does it form? water
What is gained during this process? A H+ gradient

38. Oxidative phosphorylation
What is the purpose?
What is a chemiosmotic gradient?
How does this generate ATP?

39. Oxidative phosphorylation
What is the purpose? To produce ATP from ADP
What is a chemiosmotic gradient? A difference in concentration of H+ ions across a membrane (can be used to do work)
How does this generate ATP? Flow of H+ ions through ATP synthase into mitochondrial matrix cause the ATP synthase to rotate- chemical energy converted to mechanical energy
This drives phosphorylation of ADP into ATP (ADP + inorganic phosphate)

40. ATP Synthase
Uses flow of hydrogen ions down gradient to form ATP from inorganic phosphate and ADP

41. ATP synthase video

42. Cellular Respiration

43. ATP Numbers . . . Not exact – Based on experimental data-
1 molecule glucose yields 29 ATP
NADH – 2.5 ATP, FADH2 – 1.5 ATP
NADH from glycolysis in cytosol – electrons get passed to NAD+ or FAD in mitochondrial matrix
(which carrier makes a difference in total ATP)
Also – some of the proton motive force powers mitochondrion’s uptake of pyruvate from cytosol, also transport of phosphate into mit. matrix

44. Cellular respiration efficiency – about 40% of energy from glucose gets stored in ATP
The rest of the energy is lost as heat

45. Thermoregulation Reducing efficiency of cellular respiration
Hibernating mammals – need to maintain body temperature
Have a channel protein in inner mitochondrial membrane that allows protons to flow back down concentration gradient without generating ATP
Allows for oxidation of fats to generate heat without ATP production

46. ATP without oxygen
If oxygen is not present, etc and oxidative phosphorylation can’t occur
2 ways to produce ATP:
Anaerobic respiration – prokaryotic organisms in environment without oxygen
Use another final electron acceptor rather than oxygen, i.e. sulfur
Fermentation

47. Fermentation Makes ATP through glycolysis (only 2 ATP)
NADH transfers its electrons to pyruvate, so NAD+ can be used again in glycolysis
Alcoholic fermentation – pyruvate converted to ethyl alcohol and CO2
Lactic acid fermentation – pyruvate converted to lactate

49. What about prokaryotes?
Glycolysis – cytosol
Krebs cycle – cytosol
Electron transport chain – electron carriers in plasma membrane, gradient gets generated across plasma membrane
Do not need to transport electrons (in NADH) from glycolysis into mitochondria, so can get more ATP

50. Evolution & Glycolysis
Glycolysis is widespread among organisms
Oldest fossils of bacteria 3.5 billion years old
O2 in atmosphere not until 2.7 billion years ago
Perhaps early cells got ATP just through glycolysis

51. Food Catabolism  Biosynthesis
Proteins, Carbohydrates & Fats can all be used by cellular respiration to make ATP
Biosynthesis
Intermediates in the pathway of cell. resp. can be used to synthesize molecules for the cell.

52. Control of cellular respiration
Phosphofructokinase –
Enzyme that catalyzes 3rd step of glycolysis
- commitment step for glycolysis
Allosteric enzyme
Inhibited by ATP, citrate
Stimulated by AMP