1. Energy is converted to a usable form in cell respiration.
AHL Topic 8.2
IB Biology
Miss Werba

2. TOPIC 8 – HL MOLECULAR BIOLOGY
8.1
METABOLISM
8.2
CELL RESPIRATION
8.3
PHOTOSYNTHESIS
J WERBA – IB BIOLOGY 2

3. THINGS TO COVER U.1 U.2 U.3 U.4 U.5 U.6 U.7 U.8 Statement Guidance
Cell respiration involves the oxidation and reduction of electron carriers.
U.2
Phosphorylation of molecules makes them less stable.
U.3
In glycolysis, glucose is converted to pyruvate in the cytoplasm.
- the names of the intermediate compounds are not required.
U.4
Glycolysis gives a small net gain of ATP without the use of oxygen.
U.5
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.
U.6
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 are not required.
U.7
Energy released by oxidation reactions is carried to the cristae of the mitochondria by reduced NAD and FAD.
U.8
Transfer of electrons between carriers in the electron transport chain in the membrane of the cristae is coupled to proton pumping.
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4. THINGS TO COVER U.9 U.10 U.11 A.1 S.1 S.2 Statement Guidance NOS 2.3
In chemiosmosis protons diffuse through ATP synthase to generate ATP.
U.10
Oxygen is needed to bind with the free protons to maintain the hydrogen gradient, resulting in the formation of water.
U.11
The structure of the mitochondrion is adapted to the function it performs.
A.1
Electron tomography used to produce images of active mitochondria.
S.1
Analysis of diagrams of the pathways of aerobic respiration to deduce where decarboxylation and oxidation reactions occur.
S.2
Annotation of a diagram of a mitochondrion to indicate the adaptations to its function.
NOS 2.3
Paradigm shift—the chemiosmotic theory led to a paradigm shift in the field of bioenergetics.
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5. CELL RESPIRATION
The controlled release of energy from organic compounds in cells to form ATP
Involves enzymes
Involves metabolic pathways (chains and cycles)
Involves end-product inhibition
Involves glucose
Phosphorylates to ADP to make ATP
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6. CELL RESPIRATION C6H12O6 + 6O2 – RESPIRATION –> 6CO2 + 6H2O
Respiration includes:
glycolysis
link reaction
Kreb’s cycle
Electron Transport Chain (ETC)
chemiosmosis
There’s lots to learn – so stay sharp!
= OXIDATIVE
PHOSPHORYLATION
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7. MITOCHONDRIA
U.11
S.1
If oxygen is present, the reactions move to the mitochondria.
The structure of the mitochondrion is adapted to the function it performs.
You need to be able to annotate a diagram of a mitochondrion to show the way its structure is adapted to its function.
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8. MITOCHONDRIA
U.11
S.1
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9. MITOCHONDRIA Outer mitochondrial membrane 70S ribosomes & naked DNA
Matrix
Intermembrane space
Cristae
Inner mitochondrial
membrane
Ref: Biology for the IB Diploma, Allott
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10. MITOCHONDRIA Cristae: Intermembrane space: Matrix:
U.11
S.1
Cristae:
form a large surface area
have enzymes needed for the electron transport chain embedded in their membrane
Intermembrane space:
small to allow ions to accumulate and create a concentration gradient
Matrix:
fluid containing enzymes needed for the Krebs cycle.
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11. MITOCHONDRIA
A.1
Electron tomography: technique for getting 3D structures of sub-cellular structures using electron micrographs
Technique has been used to produce images of active mitochondria
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12. 12

13. 13

14. OXIDATION & REDUCTION Oxidation Is Loss (of electrons)
Cell respiration involves different reactions that are known as redox reactions (ie. oxidation or reduction reactions)
Oxidation & reduction occur together - as one reactant is oxidised, the other is reduced.
Remember: OIL RIG
Oxidation Is Loss (of electrons)
Reduction Is Gain (of electrons)
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15. OXIDATION & REDUCTION Reduction reactions may include:
Gain of electrons
Removal of oxygen
Gain of hydrogen
Oxidation reactions may include:
Loss of electrons
Addition of oxygen
Loss of hydrogen
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16. OXIDATION & REDUCTION NAD+ + 2H+ + 2e- ⇌ NADH + H+
Cell respiration involves the oxidation and reduction of electron carriers.
What are the electron carriers in cell respiration?
NAD – Nicotinamide Adenine Dinucleotide
NAD+ + 2H+ + 2e- ⇌ NADH + H+
FAD – Flavin Adenine Dinucleotide
FAD+ + 2H+ + 2e- ⇌ FADH2
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17. CELL RESPIRATION THROUGH ART

19. Glycolysis Krebs cycle
Electron
Transport Chain
Glucose C6H12O6

20. Glycolysis Glucose C6H12O6 anaerobic 2 pyruvate (3C) Electron
Krebs cycle
Electron
Transport Chain
Glucose C6H12O6
anaerobic
aerobic
2 pyruvate (3C)

21. Glycolysis Krebs cycle Electron Transport Chain Glucose C6H12O6
anaerobic
aerobic
2 pyruvate (3C)
 2 ATP
 4 ATP
2 NADH 
2 ATP (net gain)

22. Glycolysis Krebs cycle Electron Transport Chain Glucose C6H12O6
anaerobic
aerobic
2 pyruvate (3C)
 2 ATP
 4 ATP
2 NADH 
2 lactic acid
2 ethanol + 2 CO2
Alcohol fermentation
2 ATP (net gain)
Lactate fermentation
(plants/yeast)
(animals)

23. Glycolysis 2 acetyl CoA 2 CO2 Krebs cycle Electron Transport Chain
Glucose C6H12O6
anaerobic
aerobic
2 pyruvate (3C)
 2 ATP
 4 ATP
2 NADH 
2 lactic acid
2 ethanol + 2 CO2
2 ATP (net gain)
 2 NADH
Alcohol fermentation
Lactate fermentation
(plants/yeast)
(animals)

24. Glycolysis Krebs cycle Electron Transport Chain Glucose C6H12O6
anaerobic
aerobic
2 pyruvate (3C)
 2 ATP
 4 ATP
2x NADH 
2 lactic acid
2 ethanol + 2 CO2
2 acetyl CoA
2CO2  4C
6 NADH 
2 ATP 
4 CO2 
 2 FADH2
2 ATP (net gain)
 2 NADH
Alcohol fermentation
Lactate fermentation
(plants/yeast)
(animals)

25. (2 x 3) + (2 x 1) + ( 2 x 3) + (6 x 3) + (2 x 1) + (2 x 2)
THE ETC CASINO
Let’s add up what we have and see how many chips we can get for the ETC casino
Don’t forget the link reaction!
NADH 3
FADH2 2
ATP 1
(2 x 3) + (2 x 1) + ( 2 x 3) + (6 x 3) + (2 x 1) + (2 x 2)
= 38 chips or 38 ATP

26. Glycolysis Krebs cycle Electron Transport Chain Glucose C6H12O6
anaerobic
aerobic
2 pyruvate (3C)
 2 ATP
 4 ATP
worth 6 ATP  2 NADH 
2 lactic acid
2 ethanol + 2 CO2
2 acetyl CoA
2 CO2  4C
worth 18 ATP  6 NADH 
worth 2 ATP  2 ATP 
4 CO2 
 2 FADH2  worth 4 ATP
2 ATP  worth 2 ATP (net gain)
 2 NADH  worth 6 ATP
Alcohol fermentation
Lactate fermentation
(plants/yeast)
(animals)

27. AEROBIC RESPIRATION
Aerobic cellular respiration involves four major reaction pathways:
Glycolysis  conversion of glucose to pyruvate
The Link Reaction  conversion of pyruvate to acetyl CoA
The Krebs Cycle  mitochondrion
The Electron Transport chain  chemiosmosis
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28. GLYCOLYSIS Glycolysis occurs without the use of oxygen
Occurs in the cytoplasm
One glucose molecule is converted into two pyruvate molecules.
2 ATP molecules are used but 4 ATP are produced, so there is a net yield of 2 ATP.
2 NAD+ are converted into 2 NADH + H+
You don’t need to remember the names of the intermediate compounds in glycolysis.
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29. http://www. mheducation 29

30. http://www. science. smith. edu/departments/Biology/Bio231/glycolysis 30

31. GLYCOLYSIS There are 4 main stages to Glycolysis: 1) Phosphorylation
U.3
U.4
There are 4 main stages to Glycolysis:
1) Phosphorylation
2) Lysis
3) Oxidation
4) ATP formation
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32. GLYCOLYSIS 1) Phosphorylation 2 phosphates are added to glucose
2 ATP molecules are needed to provide the phosphates
Phosphorylation of molecules makes them less stable.
2) Lysis
The 6C molecule (glucose bisphophate) is then split into two 3C molecules (triose phosphate).
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33. GLYCOLYSIS 3) Oxidation
U.3
U.4
3) Oxidation
2 hydrogen atoms are removed from each 3C molecule  NAD+ accepts them
2 phosphate groups are added to each molecule using the energy released.
4) ATP formation
2 phosphate groups are removed from each molecule  passed to ADP
This forms two molecules of pyruvate and ATP.
This is called substrate level phosphorylation.
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34. GLYCOLYSIS
U.3
U.4
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35. Glycolysis Krebs cycle Electron Transport Chain Glucose C6H12O6 G6P
anaerobic
aerobic
2x pyruvate (3C)
 2x ATP
 4x ATP
worth 6 ATP  2x NADH 
lactic acid
ethanol & CO2
fermentation
acetyl CoA
2CO2  4C
worth 18 ATP  6x NADH 
worth 2 ATP  2x ATP 
4x CO2 
 2x FADH2  worth 4 ATP
2x ATP  worth 2 ATP (net gain)
 2x NADH  worth 6 ATP

36. THE LINK REACTION
U.5
After glycolysis, pyruvate moves to the mitochondrion.
Enzymes in the mitochondrial matrix are used to:
oxidise the pyruvate remove hydrogen  NAD+ accepts it
decarboxylate the pyruvate remove carbon  CO2 is released
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37. THE LINK REACTION This conversion is called oxidative decarboxylation.
U.5
This conversion is called oxidative decarboxylation.
The product of this is an acetyl compound, which attaches to coenzyme A (CoA) to form acetyl CoA.
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38. Glycolysis Krebs cycle Electron Transport Chain Glucose C6H12O6
anaerobic
aerobic
2 pyruvate (3C)
 2 ATP
 4 ATP
worth 6 ATP  2 NADH 
2 lactic acid
2 ethanol + 2 CO2
2 acetyl CoA
CO2  4C
worth 18 ATP  6 NADH 
worth 2 ATP  2 ATP 
4 CO2 
 2 FADH2  worth 4 ATP
2 ATP  worth 2 ATP (net gain)
 2 NADH  worth 6 ATP
Alcohol fermentation
Lactate fermentation
(plants/yeast)
(animals)

39. THE KREBS CYCLE Also known as the Citric Acid Cycle
U.6
Also known as the Citric Acid Cycle
Happens in the mitochondrial matrix
Yields 2 ATP
No O2 used but process is O2-dependent
C and O from C6H12O6 are released as CO2
H is left over
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40. THE KREBS CYCLE The Krebs Cycle occurs in a number of stages:
1) C2 + C4 = C6
Acetyl CoA (C2) from the link reaction joins to oxoaloacetate (C4), forming citrate (C6)
CoA is released and recycled
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41. THE KREBS CYCLE 2) C6  C5 + CO2
U.6
2) C6  C5 + CO2
Decarboxylation – CO2 is released from citrate (C6), leaving a 5-carbon (C5) compound
Reduction – NAD+ accepts 2 H atoms  forms NADH
3) C5  C4 + CO2
Decarboxylation – CO2 is released from the C5 compound  forms a C4 compound
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42. THE KREBS CYCLE 4) ATP synthesis (substrate level phosphorylation)
ATP is synthesised from ADP
two reduction reactions:
NAD+ + 2H  NADH + H+
FAD + 2H  FADH2
Manga guide to Biochemistry 
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43. THE KREBS CYCLE One turn of the Krebs Cycle yields: 2 CO2 3 NADH + 3H+
1 FADH2
1 ATP (by substrate level phosphorylation)
Remember that there are 2 turns of the Krebs cycle for each glucose molecule!!!
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44. THE KREBS CYCLE U.6 J WERBA – IB BIOLOGY
Ref: Biology for the IB Diploma, Allott 44

45. https://youtu.be/WWZ0_cHwhX845

46. Glycolysis Krebs cycle Electron Transport Chain Glucose C6H12O6
anaerobic
aerobic
2 pyruvate (3C)
 2 ATP
 4 ATP
worth 6 ATP  2 NADH 
2 lactic acid
2 ethanol + 2 CO2
2 acetyl CoA
CO2  4C
worth 18 ATP  6 NADH 
worth 2 ATP  2 ATP 
4 CO2 
 2 FADH2  worth 4 ATP
2 ATP  worth 2 ATP (net gain)
 2 NADH  worth 6 ATP
Alcohol fermentation
Lactate fermentation
(plants/yeast)
(animals)

47. THE ELECTRON TRANSPORT CHAIN (ETC)
U.7
The reduced forms of NAD (NADH) and FAD (FADH2) carry H+ ions and electrons to the ETC.
The ETC is in the cristae – the folds of the inner mitochondrial membrane (IMM).
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48. THE ELECTRON TRANSPORT CHAIN (ETC)
U.7
The Electron Transport Chain (ETC) is composed of electron carriers embedded in the IMM.
Electrons are removed from NADH or FADH2 and passed from one carrier to another by a series of redox reactions.
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49. THE ELECTRON TRANSPORT CHAIN (ETC)
U.7
U.8
The transfer of electrons is coupled to proton pumping.
Hydrogens are pumped across the membrane to the inter-membrane space by the energy released from the electrons.
Results in a high concentration of H+ ions in the space between the membranes
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50. CHEMIOSMOSIS
U.9
U.10
In chemiosmosis, protons diffuse through ATP synthase to generate ATP.
Oxygen is needed to bind with the free protons to maintain the hydrogen gradient, resulting in the formation of water.
This occurs in the matrix of the mitochondrion.
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51. CHEMIOSMOSIS Paradigm shift
NOS.2.3
Paradigm shift
The chemiosmotic theory led to a paradigm shift in the field of bioenergetics.
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52. CHEMIOSMOSIS
NOS 2.3
In 1961, Peter Mitchell, a British biochemist, proposed the chemiosmotic theory of ATP production.
He received a Nobel prize for this work in 1978.
His ideas explained how ATP synthesis is coupled to electron transport and the movement of protons.
His ideas were different to previous explanations, but after many years, the theory was accepted.
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53. 53

54. http://highered. mheducation 54

55. CELLULAR RESPIRATION
Thus the net production of energy from aerobic respiration from ONE glucose:
Stage
ATP
Glycolysis
2 ATP used at the start
2 NADH + H+
Substrate level phosphorylation
-2 ATP
6 ATP
4 ATP
Link Reaction
Krebs cycle
6 NADH + H+
2FADH2
2 ATP
18 ATP
Net Yield of ATP
38 ATP
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56. Glycolysis Krebs cycle Electron Transport Chain Glucose C6H12O6
anaerobic
aerobic
2 pyruvate (3C)
 2 ATP
 4 ATP
worth 6 ATP  2 NADH 
2 lactic acid
2 ethanol + 2 CO2
2 acetyl CoA
CO2  4C
worth 18 ATP  6 NADH 
worth 2 ATP  2 ATP 
4 CO2 
 2 FADH2  worth 4 ATP
2 ATP  worth 2 ATP (net gain)
 2 NADH  worth 6 ATP
Alcohol fermentation
Lactate fermentation
(plants/yeast)
(animals)

57. CELL RESPIRATION
Q1. During glycolysis, a hexose sugar is broken down to two pyruvate molecules. What is the correct sequence of stages? A. phosphorylation → oxidation → lysis B. oxidation → phosphorylation → lysis C. phosphorylation → lysis → oxidation D. lysis → oxidation → phosphorylation
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58. CELL RESPIRATION
Q2. What is the role of NADH + H+ in aerobic cell respiration? A. To transfer hydrogen to the electron transport chain B. To reduce intermediates in the Krebs cycle C. To accept electrons from the electron transport chain D. To combine with oxygen to produce water
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59. CELL RESPIRATION
Q3. a) Indicate two places where decarboxylation occurs. (1) b) Explain why the given places were selected. (1) Q4. Explain the link reaction that occurs between glycolysis and the Krebs cycle. [4]
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60. CELL RESPIRATION
Q5. The enzyme ATP synthase has an essential role in aerobic cell respiration.
Describe its location. [1]
Describe its function. [1]
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