1. Cellular Respiration Chapter 9

2. Energy Flow Review

3. Review: Oxidation and Reduction
Oxidized atom
Electron is donated
Energy is donated
Reduced atom
Electron is received
Energy is received 49

4. Review: Oxidation and Reduction
This atom served as an energy carrier. It picked up an electron from the atom on the left and gave it to the one on the right.
Oxidized atom
Electron is donated
Energy is donated
Reduced atom
Electron is received
Energy is received 49

5. Why celluar respiration?
Cells carry out the reactions of cellular respiration in order to produce ATP. ATP is used by the cells for energy.
All organisms need energy, therefore all organisms carry out cellular respiration.
The energy needed to produce ATP comes from glucose, produced by photosynthesis.
The equation for cellular respiration is: C6H12O6 + 6O2  6CO2 + 6H2O + 36 ATP reverse of the equation for photosynthesis.

6. C6H12O6 + 6O2  6CO2 + 6H2O + 36 ATP Cellular Respiration
The electrons (hydrogen atoms) in glucose will be passed to oxygen to form water.
Will be oxidized
During cellular respiration, the electrons (hydrogen atoms) in glucose will be removed in a number of steps
During this process, ATP will be produced.
Will be reduced
Substrate Level Phosphorylation 5

7. C6 etc.
In the slides that follow, the designations listed below will be used.
C6 = a molecule that contains six-carbon atoms (example: Glucose)
C5 = a five-carbon molecule
C4 = a four-carbon molecule
C3 = a three-carbon molecule
C2 = a two-carbon molecule
C1 = a one-carbon molecule (example: CO2)
Each of these (C6, C5, etc.) also have hydrogen and oxygen atoms but these will be ignored.
Three parts of Cellular Respiration
Glycolysis
Formation of Acetyl CoA to Krebs Cycle
Electron Transport System

8. First Part of Cellular Respiration
glycolysis
Glucose
2 ATP
2 Pyruvate
The first step is called glycolysis. It occurs in the cytoplasm of the cell
During glycolysis, a glucose molecule (6 carbons) is converted to two pyruvate molecules (3 carbons each).
It does not require oxygen (it is anaerobic).
A total of 2 ATP are gained as a result of these reactions.
(2 ATP used, 4 ATP made, Net of 2 ATP)
Details of these reactions will be discussed later. 6

9. Two Possible Directions to Go
Fermentation occurs if there is no oxygen present.
It does not produce additional ATP.
Glucose
2 Pyruvate
2 ATP
No oxygen
Oxygen
Aerobic respiration
34 more
ATP
0 ATP
Aerobic respiration occurs in the mitochondrion.
It requires oxygen (it is aerobic).
It produces an additional 34 ATP.
Fermentation
The waste products of fermentation are alcohol or lactate.
Alcohol + CO2
(yeast, plants)
Lactate
(animals) 7

10. Glycolysis - Details glucose (C6) 2 ATP 2 ADP 2C3 2 pyruvate (C3)
Two ATP are consumed during glycolysis.
Several different 3-carbon compounds are produced during the reactions. The designation “C3” is used here to represent all of them. Be aware that in addition to carbon, these compounds also contain oxygen and hydrogen.
Glycolysis consists of a number of different reactions that produce 2 pyruvate molecules from one glucose molecule. 10

11. Glycolysis glucose (C6) 2 ATP 2 ADP 2C3 2 ADP 2 ATP 2 pyruvate (C3)
Four ATP are produced. As a result, there is a net gain of two ATP.
2 ADP
2 ATP
The ATP are produced by substrate-level phosphorylation.
2 pyruvate (C3) 14

12. Glycolysis 4 ATP produced - 2 ATP consumed 2 ATP net
glucose (C6)
4 ATP produced
- 2 ATP consumed
2 ATP net
2 NADH are also produced
2 ATP
2 ADP
2C3
2 NAD+
2 NADH
2 NAD+
2 NADH
NAD+ picks up two electrons to become NADH.
2 ADP
2 ATP
The goal of cellular respiration is to produce ATP. NADH contains energy that can be used to produce ATP. This will be discussed later. Click here to review Glycolysis
2 ADP
2 ATP
2 pyruvate (C3) 14

13. Occurs in Cytosol of the Cell
glucose (C6)
Glycolysis
2 ATP
2 ADP + P
2 C3
2 NAD+
2 ADP + P
2 NADH
2 ATP
2 ADP + P
2 ATP
2 pyruvate (C3)
Occurs in Cytosol of the Cell
Click here to review NADH, a carrier of an electron
This diagram summarizes glycolysis. As the discussion of cellular respiration proceeds, we will add to this diagram. 11

14. Formation of Acetyl CoA: Transport protein/enzyme
Needs Enzyme, Acetyl Coenzyme A
Uses Transport Protein to enter Matrix of Mitochondria
2 CO2
Coenzyme A
Will Enter Krebs Cycle
(C3H3O3)
2 pyruvate
(C3)
(C2H3O – S – CoA)
2 acetyl CoA
(C2)
2 NAD+
2 NADH
During this step, the pyruvate that was produced by glycolysis is converted to acetyl CoA by the removal of CO2. Pyruvate is a C3, acetyl CoA is a C2.
Two NAD+ molecules pick up two electrons each to become NADH. 16

15. Glycolysis Formation of Acetyl CoA
glucose (C6)
Glycolysis
2 ATP
2 ADP + P
2 C3
2 NAD+
Formation of
Acetyl CoA
2 ADP + P
2 NADH
2 ATP
2 ADP + P
2 CO2
2 ATP
2 pyruvate (C3)
2 acetyl groups (C2)
2 NAD+
2 NADH
This diagram summarizes glycolysis and the formation of acetyl CoA. 11

16. Cyclic Metabolic Pathways
The Krebs Cycle is a cyclic pathway.
Click here to review
cyclic pathways

17. Krebs Cycle: per Glucose
2 C2 (acetyl CoA)
2 Coenzyme A
2 C4
2 C6
(C6H5O7)
The acetyl portion of acetyl CoA becomes bonded to a C4 molecule to produce a C6 molecule.
The above diagram is represented by the equation below:
Acetyl CoA + C4  C6 + Coenzyme A 18

18. Krebs Cycle: per glucose
2 C2 (acetyl CoA)
2 NAD+
2 NADH
2 C6
2 C5
2 CO2
NADH is also produced from NAD+.
2 C4
CO2 has only one carbon (C1). The oxygen in CO2 came from the C6 molecule.
A CO2 is removed from the C6 molecule to produce a C5 molecule. 19

19. Krebs Cycle: per glucose
2 C2 (acetyl CoA)
six more NADH, two FADH2, and two ATP are produced.
2 C6
Another CO2 is then released.
2 NADH
2 C4
2 CO2
2 C5
2 CO2
2 NAD
2 FADH+
2 NADH
2 FADH2
2 NAD
2 NADH
2 ADP
2ATP 20

20. Krebs Cycle: per glucose
2 C2 (acetyl CoA)
2 C6
2 NADH
2 C4
2 CO2
2 C5
2 CO2
2 NADH
2 ATP
2 NADH
2 FADH2
The ATP is produced by substrate-level phosphorylation. 20

21. Summary of the Krebs Cycle PER Pyruvate
Acetyl CoA enters the Krebs cycle.
The two carbon atoms are released in the form of CO2. C2 C6
NADH C4
CO2 C5
CO2
NADH
ATP
NADH
FADH2 20

22. Summary of the Krebs Cycle Per Pyruvate
C2 (acetyl CoA) C6
Three NADH, one FADH2 and one ATP are produced for each acetyl group (C3).
NADH C4
CO2 C5
CO2
NADH
ATP
NADH
FADH2
Remember 2 C2 (acetyl CoA) are formed per Glucose 20

23. Glycolysis Krebs Cycle Formation of Acetyl CoA 2 NADH 2 ATP (net)
glucose (C6)
Glycolysis
2 ATP
2 ADP + P
Krebs Cycle
2 C3
2 NAD+
Formation of
Acetyl CoA
2 ADP + P
2 NADH
2 ATP
2 C2 (acetyl CoA)
2 ADP + P
2 C6
2 CO2
2 NADH
2 ATP
2 pyruvate (C3)
2 acetyl groups (C2)
2 C4
2 CO2
2 C5
2 NAD+
2 NADH
2 NADH
2 CO2
2 NADH
2 ATP (net)
2 ATP
2 FADH2
2 NADH
2NADH
Summary:
10 NADH
4 ATP
2 FADH2
6 NADH
2 ATP
2 FADH2 11

24. Electron Transport System
NADH and FADH2 produced during these reactions can be used to produce ATP.
The production of ATP using NADH and FADH2 involves the electron transport system, a system of proteins located on the inner membrane of the mitochondria.

25. Mitochondrion Structure
This drawing shows a mitochondrion cut lengthwise to reveal its internal components.
Intermembrane Space
Cristae Matrix

26. Mitochondrion outside inside intermembrane space
These red dots represent proteins in the electron transport system
inside
intermembrane
space 25

27. Mitochondrion H+ H+ H+ H+ H+ H+ NADH e- H+ H+ H+ H+ H+ H+ H+ H+
NADH and FADH2 from cellular respiration bring electrons to the electron transport system.
NADH e- H+ H+ H+ H+ H+ H+ H+ H+ 26

28. Mitochondrion H+ H+ H+ H+ H+ H+ e- H+ H+ H+ H+ H+ H+ H+ H+
When a carrier is reduced, some of the energy that is gained as a result of that reduction is used to pump hydrogen ions across the membrane into the intermembrane space. e- H+ H+ H+ H+ H+ H+ H+ H+ 27

29. Mitochondrion H+ H+ H+ H+ H+ e- H+ H+ H+ H+ H+ H+ H+ H+ H+
The electron is then passed to another carrier. e- H+ H+ H+ H+ H+ H+ H+ H+ H+ 28

30. Mitochondrion H+ H+ H+ H+ H+ e- H+ H+ H+ H+ H+ H+ H+ H+ H+
As before, some of the energy gained by the next carrier as a result of reduction is used to pump hydrogen ions into the intermembrane space. e- H+ H+ H+ H+ H+ H+ H+ H+ H+ 29

31. Mitochondrion H+ H+ H+ H+ e- H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ 30

32. Mitochondrion H+ H+ H+ H+ H+ e- H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ 31

33. Mitochondrion H+ H+ H+ H+ e- H+ H+ H+ H+ H+ H+ H+ H+ H+ H+
Eventually, a concentration gradient of hydrogen ions is established in the intermembrane space (green on the diagram). e- H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ 32

34. H+ Mitochondrion H+ H+ H+ H+ e- H+ H+ H+ H+ H+ H+ H+ H+
The last carrier must get rid of the electron. It passes it to oxygen to form water (next slide). e- H+ H+ H+ H+ H+ H+ H+ H+ H+ 34

35. Mitochondrion H+ H+ H+ H+ 2H+ + 2e- + 1/2 O2  H2O H+ H+ H+ H+ H+ H+
Note that e- + H+  H
Mitochondrion H+ H+ H+ H+
Two electrons are required to form one molecule of water. The process therefore happens twice for each water molecule.
2H+ + 2e- + 1/2 O2  H2O H+ H+ H+ H+ H+ H+ H+ H+ H+ 34

36. Mitochondrion H+ H+ H+ H+ H+ H+ H+ H+ ADP + Pi H+ H+ ATP H+ H+ H+ H+
ATP synthase produces ATP by phosphorylating ADP. The energy comes from hydrogen ions forcing their way into the matrix as they pass through the ATP synthase (due to osmotic pressure).
ADP + Pi H+ H+ H+
ATP H+ H+ H+ H+ 33

37. Summary of Oxidative Phosphorylation
2H+ + 2e- + 1/2 O2  H2O
NADH H+ H+ H+ H+
ADP + Pi H+ H+ H+
ATP H+ H+ H+ H+ 33

38. Glycolysis Krebs Cycle Formation of Acetyl CoA electron transport
glucose (C6)
Glycolysis
2 ATP
2 ADP + P
Krebs Cycle
2 C3
2 NAD+
Formation of
Acetyl CoA
2 ADP + P
2 NADH
2 ATP
2 C2 (acetyl CoA)
2 ADP + P
2 C6
2 CO2
2 NADH
2 ATP
2 pyruvate (C3)
2 acetyl groups (C2)
2 C4
2 CO2
2 C5
2 NAD+
2 NADH
2 NADH
2 CO2
2 ATP
2 FADH2
2 NADH
10 NAD+
2 FAD
electron
transport
1/2 O2
32 ATP
H2O 11

39. Summary of Cellular Respiration
glucose
Glycolysis
2 pyruvate
2 ATP
2 NADH

40. Summary CO2 C C C glucose Glycolysis 2 pyruvate 2 ATP 2 NADH
Acetyl CoA
2 acetyl CoA
2CO2
2NADH

41. Summary CO2 C CO2 C C glucose Glycolysis 2 pyruvate 2 ATP 2 NADH
Acetyl CoA
2 acetyl CoA
2CO2
2NADH
Krebs Cycle
4 CO2
2 ATP
6 NADH
1 FADH2

42. ATP Yield per Glucose Pathway Substrate-Level Phosphorylation
Oxidative Phosphorylation
Total ATP
Glycolysis 2
2 NADH (= 4 ATP) 6
Glycolysis occurs in the cytoplasm of the cell. NADH produced in the cytoplasm must be brought into the mitochondrion before ATP is produced. Each NADH produced in glycolysis results in 2 ATP.

43. These NADH result in the production of 2 ATP each because they are produced outside the mitochondrion and must be transported in.
ATP Yield per Glucose
Pathway
Substrate-Level Phosphorylation
Oxidative Phosphorylation
Total ATP
Glycolysis 2
2 NADH (= 4 ATP) 6
Formation of Acetyl CoA
2 NADH (= 6 ATP)
Acetyl CoA is formed in the mitochondrion. Because the NADH produced is already in the mitochondrion, each NADH results in the production of 3 ATP.

44. ATP Yield per Glucose Pathway Substrate-Level Phosphorylation
Oxidative Phosphorylation
Total ATP
Glycolysis 2
2 NADH (= 4 ATP) 6
Formation of Acetyl CoA
2 NADH (= 6 ATP)
Krebs Cycle
6 NADH (= 18 ATP)
2 FADH2 (= 4 ATP) 24

45. ATP Yield per Glucose Pathway Substrate-Level Phosphorylation
Oxidative Phosphorylation
Total ATP
Glycolysis 2
2 NADH (= 4 ATP) 6
Formation of Acetyl CoA
2 NADH (= 6 ATP)
Krebs Cycle
6 NADH (= 18 ATP)
2 FADH2 (= 4 ATP) 24
Total 4 32 36

46. glucose (C6)
Glycolysis
2 ATP
2 ADP + P
2 C3
2 NAD+
Fermentation does not involve the formation of acetyl CoA, the Krebs Cycle, or oxidative phosphorylation.
2 ADP + P
2 NADH
2 ATP
2 ADP + P
Fermentation includes glycolysis plus several additional steps.
2 ATP
2 pyruvate (C3) 11

47. Fermentation 2 ADP + Pi 2 NAD+ 2 ATP 2 NADH
Glycolysis requires a supply of NAD+.
2 ADP + Pi
2 ATP
2 NAD+
2 NADH
NADH must reduce (donate its electrons) to another molecule in order to regenerate NAD+.
Otherwise, all of the NAD+ will be used up as it is converted to NADH and glycolysis will stop. 42

48. Fermentation glucose 2 ADP + Pi 2 NAD+ 2 ATP pyruvate 2 NADH lactateor
alcohol
2 ADP + Pi
2 ATP
2 NAD+
2 NADH
NADH gives its electron to pyruvate, which is reduced to form either lactate or alcohol.
(animals, bacteria)
(plants, fungi) 43

49. Other materials used in Cellular Respiration

50. Control and Regulation of Cellular Respiration
Feed back Mechanisms
Based on supply and demand
Cell working hard, ATP concentration drops, C.R. speeds up
Glycolysis
Phosphofructokinase: control step in gylcolysis
Pacemaker of CR
Inhibited by ATP (allosteric site on enzyme)
Stimulated by AMP
Sensitive to Citrate from Krebs Cycle

51. The End Or
Is It?

52. Substrate-Level Phosphorylation
Phosphate groups
High-energy molecule
ADP
Enzyme

53. Substrate-Level Phosphorylation

54. Substrate-Level Phosphorylation
Low-energy molecule
ATP
RETURN

55. NAD+ (Nicotinamide Adenine Dinucleotide)
Organic Molecule
Organic Molecule
NAD+ + + +
NAD+ + 2H  NADH + H+
NAD+ functions in cellular respiration by carrying two electrons. With two electrons, it becomes NADH.
NAD+ oxidizes its substrate by removing two hydrogen atoms. One of the hydrogen atoms bonds to the NAD+. The electron from the other hydrogen atom remains with the NADH molecule but the proton (H+) is released. 
NAD+ + 2H ® NADH + H+
NADH then donate the two electrons (one of them is a hydrogen atom) to another molecule.
RETURNSlide 15

56. Review: NAD+ + 2H  NADH + H+
Energy + 2H
Energy + 2H
NAD+
NAD+ is an electron carrier.
RETURN 53

57. Review: A Cyclic Metabolic Pathway
A + F  B
B  C  D
D  F + E F C D E
RETURN 7