1. 8.2 Cell Respiration (AHL)
Essential idea: Energy is converted to a usable form in cell respiration.
ATP is made most commonly oxidative phosphorylation is used. The key component in this process is ATP synthase (below). This enzyme sits embedded within the inner membrane of mitochondria. When hydrogen ions flow through ATP synthase the motive force is used to convert ADP and phosphate into ATP.
Adenosine triphosphate (ATP) is the energy currency of cells. It is unstable and will breakdown into Adenosine diphosphate (ADP) and a phosphate releasing energy (as heat). The energy released by ATP is held in the bond between the second and the third phosphates. ATP can therefore be used as a coenzyme in many parts of the cells metabolism providing the energy needed for many reactions. Because of it's unstable nature it is only produced when needed. The purpose of cell respiration therefore it to breakdown carbohydrates and lipids so that ATP can be produced.
By Chris Paine

2. Understandings Statement Guidance 8.2.U1
Cell respiration involves the oxidation and reduction of electron carriers.
8.2.U2
Phosphorylation of molecules makes them less stable.
8.2.U3
In glycolysis, glucose is converted to pyruvate in the cytoplasm.
The names of the intermediate compounds in gylcolysis is not required.
8.2.U4
Glycolysis gives a small net gain of ATP without the use of oxygen.
8.2.U5
In aerobic cell respiration pyruvate is decarboxylated and oxidized, and converted into acetyl compound and attached to coenzyme A to form acetyl coenzyme A in the link reaction.
8.2.U6
In the Krebs cycle, the oxidation of acetyl groups is coupled to the reduction of hydrogen carriers, liberating carbon dioxide.
The names of the intermediate compounds in the Krebs cycle is not required.
8.2.U7
Energy released by oxidation reactions is carried to the cristae of the mitochondria by reduced NAD and FAD.
8.2.U8
Transfer of electrons between carriers in the electron transport chain in the membrane of the cristae is coupled to proton pumping.
8.2.U9
In chemiosmosis protons diffuse through ATP synthase to generate ATP.
8.2.U10
Oxygen is needed to bind with the free protons to maintain the hydrogen gradient, resulting in the formation of water.
8.2.U11
The structure of the mitochondrion is adapted to the function it performs.

3. Applications and Skills
Statement
Guidance
8.2.A1
Electron tomography used to produce images of active mitochondria.
8.2.S1
Analysis of diagrams of the pathways of aerobic respiration to deduce where decarboxylation and oxidation reactions occur.
8.2.S2
Annotation of a diagram of a mitochondrion to indicate the adaptations to its function.

8. chemiosmosis
Respiration consists of several different interlinked metabolic pathways.

9. + = chemiosmosis chemiosmosis electron transport oxidative
phosphorylation
electron
transport
chemiosmosis +
chemiosmosis
Respiration consists of several different interlinked metabolic pathways.

11. 8.2.U11 The structure of the mitochondrion is adapted to the function it performs. 8.2.S2 Annotation of a diagram of a mitochondrion to indicate the adaptations to its function.

12. 8.2.U11 The structure of the mitochondrion is adapted to the function it performs. 8.2.S2 Annotation of a diagram of a mitochondrion to indicate the adaptations to its function.
Label the structures:

13. Label the structures: matrix Inter-membrane space cristae ribosomes
8.2.U11 The structure of the mitochondrion is adapted to the function it performs. 8.2.S2 Annotation of a diagram of a mitochondrion to indicate the adaptations to its function.
Label the structures:
matrix
Inter-membrane space
cristae
ribosomes
inner membrane
outer membrane
naked loops of DNA

14. 8.2.U11 The structure of the mitochondrion is adapted to the function it performs. 8.2.S2 Annotation of a diagram of a mitochondrion to indicate the adaptations to its function.

15. 8.2.U11 The structure of the mitochondrion is adapted to the function it performs. 8.2.S2 Annotation of a diagram of a mitochondrion to indicate the adaptations to its function.

16. 8.2.A1 Electron tomography used to produce images of active mitochondria.
Electron tomography is a technique for obtaining 3D structures of sub-cellular structures using electron micrographs.
Electron tomography is improving the understanding
of mitochondria structure and function.
Use the link to find out more:

17. 8.2.U1 Cell respiration involves the oxidation and reduction of electron carriers.
What is oxidation?

18. 8.2.U1 Cell respiration involves the oxidation and reduction of electron carriers.
What is oxidation?

19. 8.2.U1 Cell respiration involves the oxidation and reduction of electron carriers.
What is oxidation?

20. NAD+ + 2H+ + 2e- NADH + H+ NAD+ NADH + H+
8.2.U1 Cell respiration involves the oxidation and reduction of electron carriers.
Who are the electron carries in cell respiration?
The most common hydrogen carrier is NAD (Nicotinamide Adenine Dinucleotide)
reduction
NAD+ + 2H+ + 2e NADH + H+
oxidation
Use the simplified form of the equation omitting the detail of the H+ ions and electrons:
reduction
NAD NADH + H+
oxidation

21. FAD + 2H+ + 2e- FADH2 FAD FADH2
8.2.U1 Cell respiration involves the oxidation and reduction of electron carriers.
Who are the electron carries in cell respiration?
Another less frequently used hydrogen carrier is FAD (Flavin Adenine Dinucleotide).
reduction
FAD + 2H+ + 2e FADH2
oxidation
Use the simplified form of the equation omitting the detail of the H+ ions and electrons:
reduction
FAD FADH2
oxidation

22. glycolysis chemiosmosis
Respiration consists of several different interlinked metabolic pathways.

23. Glycolysis is the splitting of glucose into pyruvate
8.2.U3 In glycolysis, glucose is converted to pyruvate in the cytoplasm. 8.2.U4 Glycolysis gives a small net gain of ATP without the use of oxygen.
Glycolysis is the splitting of glucose into pyruvate
Use the animations to learn about the process of glycolysis

24. Glycolysis is the splitting of glucose into pyruvate
8.2.U3 In glycolysis, glucose is converted to pyruvate in the cytoplasm. 8.2.U4 Glycolysis gives a small net gain of ATP without the use of oxygen.
Glycolysis is the splitting of glucose into pyruvate
by substrate-level phosphorylation.

25. 8.2.U2 Phosphorylation of molecules makes them less stable.
Phosphorylation is a reaction where a phosphate group (PO43-) is added to an organic molecule
The phosphorylated molecule is less stable and therefore reacts more easily in the metabolic pathway.
The phosphate group is usually transferred from ATP
Reactions that would otherwise proceed slowly and require energy into a reaction that happens quickly releasing energy.

26. In Summary: Glycolysis is the splitting of glucose into pyruvate
8.2.U3 In glycolysis, glucose is converted to pyruvate in the cytoplasm. 8.2.U4 Glycolysis gives a small net gain of ATP without the use of oxygen.
Glycolysis is the splitting of glucose into pyruvate
In Summary:
Glycolysis occurs in cytoplasm
A hexose sugar (e.g. glucose) is phosphorylated using ATP
The hexose phosphate is then split into two triose phosphates
Oxidation occurs removing hydrogen
The hydrogen is used to reduce NAD to NADH
Four ATP are produced resulting in a net gain of two ATP
Two pyruvate molecules are produced at the end of glycolysis

27. link reaction chemiosmosis
Respiration consists of several different interlinked metabolic pathways.

28. 8.2.U5 In aerobic cell respiration pyruvate is decarboxylated and oxidized, and converted into acetyl compound and attached to coenzyme A to form acetyl coenzyme A in the link reaction.

29. 8.2.U5 In aerobic cell respiration pyruvate is decarboxylated and oxidized, and converted into acetyl compound and attached to coenzyme A to form acetyl coenzyme A in the link reaction.

30. 8.2.U5 In aerobic cell respiration pyruvate is decarboxylated and oxidized, and converted into acetyl compound and attached to coenzyme A to form acetyl coenzyme A in the link reaction.

31. 8.2.U5 In aerobic cell respiration pyruvate is decarboxylated and oxidized, and converted into acetyl compound and attached to coenzyme A to form acetyl coenzyme A in the link reaction.

32. 8.2.U5 In aerobic cell respiration pyruvate is decarboxylated and oxidized, and converted into acetyl compound and attached to coenzyme A to form acetyl coenzyme A in the link reaction.

33. In Summary: pyruvate (from glycolysis) enters the mitochondrion matrix
8.2.U5 In aerobic cell respiration pyruvate is decarboxylated and oxidized, and converted into acetyl compound and attached to coenzyme A to form acetyl coenzyme A in the link reaction.
In Summary:
pyruvate (from glycolysis) enters the mitochondrion matrix
enzymes remove one carbon dioxide and hydrogen from the pyruvate
hydrogen is accepted by NAD to form NADH
removal of hydrogen is oxidation
removal of carbon dioxide is decarboxylation
the link reaction is therefore oxidative decarboxylation
the product is an acetyl group which reacts with coenzyme A
acetyl CoA enters Krebs cycle

34. Glycolysis is not needed, but the reaction is slower.
The details are not needed, but you should be aware that fatty acids can be used in aerobic respiration.
Glycolysis is not needed, but the reaction is slower.

35. Kreb’s cycle
chemiosmosis

36. 8.2.U6 In the Krebs cycle, the oxidation of acetyl groups is coupled to the reduction of hydrogen carriers, liberating carbon
Krebs cycle reduces electron carriers in preparation for oxidative phosphorylation (carbon is released as CO2 as a by-product)
Use the animations to learn about Krebs cycle

37. 8.2.U6 In the Krebs cycle, the oxidation of acetyl groups is coupled to the reduction of hydrogen carriers, liberating carbon dioxide.

38. 8.2.U6 In the Krebs cycle, the oxidation of acetyl groups is coupled to the reduction of hydrogen carriers, liberating carbon dioxide.

39. 8.2.U6 In the Krebs cycle, the oxidation of acetyl groups is coupled to the reduction of hydrogen carriers, liberating carbon dioxide.

40. 8.2.U6 In the Krebs cycle, the oxidation of acetyl groups is coupled to the reduction of hydrogen carriers, liberating carbon dioxide. H+

41. 8.2.U6 In the Krebs cycle, the oxidation of acetyl groups is coupled to the reduction of hydrogen carriers, liberating carbon dioxide.
NADH H+

42. 8.2.U6 In the Krebs cycle, the oxidation of acetyl groups is coupled to the reduction of hydrogen carriers, liberating carbon dioxide.

43. 8.2.U6 In the Krebs cycle, the oxidation of acetyl groups is coupled to the reduction of hydrogen carriers, liberating carbon dioxide.

44. 8.2.U6 In the Krebs cycle, the oxidation of acetyl groups is coupled to the reduction of hydrogen carriers, liberating carbon dioxide.

45. 8.2.U6 In the Krebs cycle, the oxidation of acetyl groups is coupled to the reduction of hydrogen carriers, liberating carbon dioxide.

46. 8.2.U7 Energy released by oxidation reactions is carried to the cristae of the mitochondria by reduced NAD and FAD.
The reduced forms of NAD and FAD carry H+ ions and electrons to the electron transport chain, is which is situated in the folds on the inner membrane, i.e. the cristae.

47. In Summary: acetyl CoA enters the Krebs cycle
8.2.U6 In the Krebs cycle, the oxidation of acetyl groups is coupled to the reduction of hydrogen carriers, liberating carbon dioxide.
In Summary:
acetyl CoA enters the Krebs cycle
acetyl group (2C) joins a 4C sugar to form a 6C sugar
oxidative decarboxylation of the 6C sugar to a 5C compound produces CO2
oxidative decarboxylation of the 5C compound to a 4C compound produces CO2
The process is oxidative as NAD and FAD are reduced by the addition of hydrogen
two CO2 are produced per molecule of pyruvate / cycle
along with three NADH + H+ and one FADH2 per molecule of pyruvate / cycle
one ATP is produced by substrate level phosphorylation (from ADP + Pi) per molecule of pyruvate / cycle
NADH and FADH2 provide electrons to the electron transport chain

48. electron
transport
chain
chemiosmosis

49. Oxidative phosphorylation part I: electron transport chain (ETC)
8.2.U8 Transfer of electrons between carriers in the electron transport chain in the membrane of the cristae is coupled to proton pumping.
Oxidative phosphorylation part I:
electron transport chain (ETC)
The process of oxidative phosphorylation happens across the inner membrane
Inter-membrane space
Inner
membrane
matrix
A series of integral protein complexes act as electron carriers forming the electron transport chain

50. Oxidative phosphorylation part I: electron transport chain (ETC)
8.2.U8 Transfer of electrons between carriers in the electron transport chain in the membrane of the cristae is coupled to proton pumping.
Oxidative phosphorylation part I:
electron transport chain (ETC)

51. Oxidative phosphorylation part I: electron transport chain (ETC)
8.2.U8 Transfer of electrons between carriers in the electron transport chain in the membrane of the cristae is coupled to proton pumping.
Oxidative phosphorylation part I:
electron transport chain (ETC)

52. Oxidative phosphorylation part I: electron transport chain (ETC)
8.2.U8 Transfer of electrons between carriers in the electron transport chain in the membrane of the cristae is coupled to proton pumping.
Oxidative phosphorylation part I:
electron transport chain (ETC)

53. Oxidative phosphorylation part I: electron transport chain (ETC)
8.2.U8 Transfer of electrons between carriers in the electron transport chain in the membrane of the cristae is coupled to proton pumping.
Oxidative phosphorylation part I:
electron transport chain (ETC)

54. chemiosmosis

55. 8.2.U9 In chemiosmosis protons diffuse through ATP synthase to generate ATP.

56. 8.2.U9 In chemiosmosis protons diffuse through ATP synthase to generate ATP.
This is the diffusion of ions across a semi-permeable membrane, through ATP synthase.
Here the ions are protons (H+) and the transmembrane (integral) protein through which they flow is the enzyme ATP synthase. This enzyme catalyses the reaction ADP + Pi  ATP. The flow of H+ is used to generate ATP.

57. Oxidative phosphorylation part II:
8.2.U9 In chemiosmosis protons diffuse through ATP synthase to generate ATP.
Oxidative phosphorylation part II:
chemiosmosis

58. Oxidative phosphorylation part II:
8.2.U9 In chemiosmosis protons diffuse through ATP synthase to generate ATP.
Oxidative phosphorylation part II:
chemiosmosis
This creates an electrochemical gradient.
The yield of ATP from chemiosmosis is potentially 32 molecules, but in most conditions the yield is slightly lower.

59. Nature of Science: Paradigm shift—the chemiosmotic theory led to a paradigm shift in the field of bioenergetics. (2.3)
In 1961 Peter Mitchell proposed the chemiosmotic theory.
His ideas explained how synthesis is coupled to electron transport and proton movement.
His ideas were very different to previous explanations.
It takes time for scientists working in a field to accept paradigm shifts, even when there is strong evidence.
After many years the theory was accepted. Peter Mitchell received the Nobel Prize for Chemistry in 1978
Find out more:

60. Oxidative phosphorylation part I: electron transport chain (ETC)
8.2.U10 Oxygen is needed to bind with the free protons to maintain the hydrogen gradient, resulting in the formation of water.
Oxidative phosphorylation part I:
electron transport chain (ETC)

61. Oxidative phosphorylation part I: electron transport chain (ETC)
8.2.U10 Oxygen is needed to bind with the free protons to maintain the hydrogen gradient, resulting in the formation of water.
Oxidative phosphorylation part I:
electron transport chain (ETC)

62. A summary of oxidative phosphorylation (8.2.U8 – 8.2.U10)
Use the animations to learn to check your understanding of oxidative phosphorylation.

63. A summary of oxidative phosphorylation (8.2.U8 – 8.2.U10)

64. A summary of oxidative phosphorylation (8.2.U8 – 8.2.U10)
the electron transport chain is situated on the inner mitochondrial membrane
hydrogen is transferred to the electron transport chain by hydrogen carriers, i.e. NADH and FADH2
The hydrogen carriers release electrons which are transferred between carriers this releases energy …
…. which is used to pump H+ ions (from the matrix) across inner membrane
H+ ions to accumulate in the inter-membrane space creating a concentration gradient
H+ ions return to the matrix through ATP synthase
Down the electrochemical concentration gradient
This produces ATP by chemiosmosis
oxygen is the final electron acceptor for the electron transport chain
oxygen combines with electrons and H+ ions to produce water

65. Indicate two places where decarboxylation occurs. (1)
8.2.S1 Analysis of diagrams of the pathways of aerobic respiration to deduce where decarboxylation and oxidation reactions occur.
Indicate two places where decarboxylation occurs. (1)
Explain why the given places where selected. (1)

66. Indicate two places where decarboxylation occurs. (1)
8.2.S1 Analysis of diagrams of the pathways of aerobic respiration to deduce where decarboxylation and oxidation reactions occur.
Indicate two places where decarboxylation occurs. (1)
Explain why the given places where selected. (1)
decarboxylation
The molecule reduces the number of carbon atoms it contains in each place, therefore each reaction must be a decarboxylation.
decarboxylation
decarboxylation

67. 8.2.S1 Analysis of diagrams of the pathways of aerobic respiration to deduce where decarboxylation and oxidation reactions occur.
The diagram shows the three stages of glycolysis. Which processes are indicated by I, II and III? I II
III A
Lysis
Phosphorylation
Oxidation and ATP formation B C D

68. 8.2.S1 Analysis of diagrams of the pathways of aerobic respiration to deduce where decarboxylation and oxidation reactions occur.
The diagram shows the three stages of glycolysis. Which processes are indicated by I, II and III? I II
III A
Lysis
Phosphorylation
Oxidation and ATP formation B C D

69. Annotate the labelled structures:
8.2.U11 The structure of the mitochondrion is adapted to the function it performs. 8.2.S2 Annotation of a diagram of a mitochondrion to indicate the adaptations to its function.
Annotate the labelled structures:
matrix
Now you know the processes and where they happen
Inter-membrane space
cristae
ribosomes
inner membrane
outer membrane
naked loops of DNA

70. Annotate the labelled structures:
8.2.U11 The structure of the mitochondrion is adapted to the function it performs. 8.2.S2 Annotation of a diagram of a mitochondrion to indicate the adaptations to its function.
Annotate the labelled structures:
matrix
fluid containing enzymes  for the Krebs cycle and the link reaction.
Inter-membrane space
Small space  H+ ions pumped into the space quickly generate a high concentration gradient for chemiosmosis.
Folds in the innner membrane  increase surface area available for oxidative phosphorylation
cristae
ribosomes
inner membrane
Synthesises proteins, including enzymes used in aerobic respiration.
contains the integral proteins that make up the electron transport chain and ATP synthase  electron transport and chemiosmosis
outer membrane
naked loops of DNA
contains the contents of the mitochondrion  enables optimal conditions for aerobic respiration
Necessary mitochondria function, including protein synthesis

71. Bibliography / Acknowledgments
Jason de Nys