1. 2.8 Cell Respiration
Essential idea: Cell respiration supplies energy for the functions of life.
Energy in cells is all about the molecule shown, Adenosine Triphosphate (ATP). The energy is held in the bonds between atoms, in particular the high energy bond that joins the second and third phosphates. ATP is the energy currency of the cell. Hence the efficiency of respiration is measured by the yield of ATP.
By Chris Paine

2. Understandings, Applications and Skills
Statement
Guidance
2.8.U1
Cell respiration is the controlled release of energy from organic compounds to produce ATP.
Details of the metabolic pathways of cell respiration are not needed but the substrates and final waste products should be known.
2.8.U2
ATP from cell respiration is immediately available as a source of energy in the cell.
2.8.U3
Anaerobic cell respiration gives a small yield of ATP from glucose.
2.8.U4
Aerobic cell respiration requires oxygen and gives a large yield of ATP from glucose.
2.8.A1
Use of anaerobic cell respiration in yeasts to produce ethanol and carbon dioxide in baking.
2.8.A2
Lactate production in humans when anaerobic respiration is used to maximize the power of muscle contractions.
2.8.S1
Analysis of results from experiments involving measurement of respiration rates in germinating seeds or invertebrates using a respirometer.
There are many simple respirometers which could be used. Students are expected to know that an alkali is used to absorb CO2, so reductions in volume are due to oxygen use. Temperature should be kept constant to avoid volume changes due to temperature fluctuations.

4. 2.8.U1 Cell respiration is the controlled release of energy from organic compounds to produce ATP.

5. 2.8.U1 Cell respiration is the controlled release of energy from organic compounds to produce ATP.
Chemical energy stored in bonds

6. 2.8.U1 Cell respiration is the controlled release of energy from organic compounds to produce ATP.

7. 2.8.U1 Cell respiration is the controlled release of energy from organic compounds to produce ATP.

8. 2.8.U1 Cell respiration is the controlled release of energy from organic compounds to produce ATP.

9. 2.8.U1 Cell respiration is the controlled release of energy from organic compounds to produce ATP.

10. 2.8.2 ATP from cell respiration is immediately available as a source of energy in the cell.

11. 2.8.1 Cell respiration is the controlled release of energy from organic compounds to produce ATP.

12. 2.8.U2 ATP from cell respiration is immediately available as a source of energy in the cell.

13. 2.8.2 ATP from cell respiration is immediately available as a source of energy in the cell.
Hydrolysis of ATP to ADP is an exothermic process (energy is released for cellular use and is ultimately converted to heat)

14. 2.8.2 ATP from cell respiration is immediately available as a source of energy in the cell.

15. 2.8.U2 ATP from cell respiration is immediately available as a source of energy in the cell.

16. 2.8.U2 ATP from cell respiration is immediately available as a source of energy in the cell.
All processes release heat energy and hence all energy eventually ends up as heat.
The heat energy initially can be used to raise the temperature of the organism, …
… but eventually it is lost to the environment and cannot be used for metabolic processes.

17. This links to 2.5 Enzymes and 8.1 Metabolism (AHL)
2.8.U1 Cell respiration is the controlled release of energy from organic compounds to produce ATP.
This links to 2.5 Enzymes and 8.1 Metabolism (AHL)

18. 2.8.U4 Aerobic cell respiration requires oxygen and gives a large yield of ATP from glucose.

19. What are the stages of cellular respiration?
Glycolysis
The Krebs Cycle
The Electron Transport Chain

20. Where does cellular respiration take place?
It actually takes place in two parts of the cell:
Glycolysis occurs in the Cytoplasm
Krebs Cycle & ETC Take place in the Mitochondria

21. Diagram of Respiration

22. Glycolysis Summary Overall production of 2 ATP
Takes place in the Cytoplasm
Anaerobic (Doesn’t Use Oxygen)
Overall production of 2 ATP
Glucose split into two molecules of Pyruvate or Pyruvic Acid (3 Carbon Sugars)

23. A Little Krebs Cycle History
Discovered by Hans Krebs in 1937
He received the Nobel Prize in physiology or medicine in 1953 for his discovery
Forced to leave Germany prior to WWII because he was Jewish

24. 2nd Stage: Krebs Cycle Summary
Requires Oxygen (Aerobic)
Produces 2 ATP’s
Cyclical series of reactions that give off CO2 and produce one ATP per cycle.
Turns twice per glucose molecule
Takes place in matrix of mitochondria

25. Krebs Cycle
NETS: 3NADH, 1ATP, 1FADH2, & 2CO2
ATP

26. 3rd Stage: Electron Transport Chain
34 ATP Produced (by far the most)
H2O Produced
Occurs Across Inner Mitochondrial membrane

27. Overall Result ATP Production: Glycolysis- 2 Kreb’s Cycle- 2
Electron Transport Chain- 34
Total- 38

28. Anaerobic Cell Respiration

29. 2.8.3 Anaerobic cell respiration gives a small yield of ATP from glucose.

30. GLYCOLYSIS (Glucose – Splitting!)
2.8.3 Anaerobic cell respiration gives a small yield of ATP from glucose.
GLYCOLYSIS (Glucose – Splitting!)

31. 2.8.3 Anaerobic cell respiration gives a small yield of ATP from glucose.

32. 2.8.3 Anaerobic cell respiration gives a small yield of ATP from glucose.

33. 2.8.3 Anaerobic cell respiration gives a small yield of ATP from glucose.

34. 2.8.3 Anaerobic cell respiration gives a small yield of ATP from glucose.

35. 2.8.3 Anaerobic cell respiration gives a small yield of ATP from glucose.

36. Anaerobic Respiration Summary:
2.8.3 Anaerobic cell respiration gives a small yield of ATP from glucose.
Anaerobic Respiration Summary:
Yields 2 ATP per glucose (from Glycolysis)
No oxygen needed
IN ANIMALS:
Glucose  Lactate + 2 ATP
IN YEAST & PLANTS:
Glucose  Ethanol + Carbon Dioxide + 2 ATP
Happens in Cytoplasm
Useful for…
Short, rapid bursts of ATP production
When oxygen supplies are low (i.e. intense exercise)
In low-oxygen environments (i.e. waterlogged soil)

37. 2.8.5 Use of anaerobic cell respiration in yeasts to produce ethanol and carbon dioxide in baking.
Yeast is a unicellular fungus that can respire aerobically or anaerobically Anaerobic respiration in yeast (aka Alcohol Fermentation) is used to produce ethanol which is the basis of most alcoholic beverages as well as bioethanol fuels (from sugar cane and corn)

38. 2.8.5 Use of anaerobic cell respiration in yeasts to produce ethanol and carbon dioxide in baking.
Anaerobic respiration in yeast also makes it a useful leavening agent in baking. Carbon dioxide released from respiration creates air bubbles in dough, causing it to rise. The ethanol by-product evaporates during baking.

39. 2.8.6 Lactate production in humans when anaerobic respiration is used to maximize the power of muscle contractions.
Anaerobic respiration in humans (aka Lactic Acid fermentation) can supply additional ATP, quickly, for a short period when oxygen is low
An adaptation that allowed early humans to escape predators
Lactate (lactic acid) builds up in muscle tissue until max limit. Oxygen must be absorbed to break it down (oxygen debt)

40. 2.8.4 Aerobic cell respiration requires oxygen and gives a large yield of ATP from glucose.

41. 2.8.4 Aerobic cell respiration requires oxygen and gives a large yield of ATP from glucose.

42. 2.8.4 Aerobic cell respiration requires oxygen and gives a large yield of ATP from glucose.

43. 2.8.4 Aerobic cell respiration requires oxygen and gives a large yield of ATP from glucose.

44. Aerobic Respiration Summary:
2.8.4 Aerobic cell respiration requires oxygen and gives a large yield of ATP from glucose.
Aerobic Respiration Summary:
Yields 36 ATP per glucose (from Glycolysis as well as following chemical reactions)
Oxygen needed
Glucose + Oxygen  Water + Carbon Dioxide + 36 ATP
Happens in Mitochondria

48. Respirometer: A device used to measure respiration rate. Most involve:
2.8.7 Analysis of results from experiments involving measurement of respiration rates in germinating seeds or invertebrates using a respirometer.
Respirometer: A device used to measure respiration rate. Most involve:
A sealed container to contain living tissue
An alkali (i.e. KOH) to absorb carbon dioxide
A capillary tube or pipette connected to the container
As oxygen is used up, the fluid moves toward the container

49. A Respirometer could be used to measure…
2.8.7 Analysis of results from experiments involving measurement of respiration rates in germinating seeds or invertebrates using a respirometer.
A Respirometer could be used to measure…
Respiration rates of different organisms
Effect of temperature on respiration
Comparing respiration in active v. inactive organisms

50. You should aim to carry out your own investigation
2.8.S1 Analysis of results from experiments involving measurement of respiration rates in germinating seeds or invertebrates using a respirometer.
The diagram shows the design of a typical respirometer. They vary greatly in their design, but all can be used to calculate the rate of respiration by measuring the consumption of oxygen.
You should aim to carry out your own investigation
In the absence of equipment you can use the worksheet (Q1-10) with the virtual lab:

51. 2.8.U3 Anaerobic cell respiration gives a small yield of ATP from glucose.

52. 2.8.U3 Anaerobic cell respiration gives a small yield of ATP from glucose.

53. 2.8.A1 Use of anaerobic cell respiration in yeasts to produce ethanol and carbon dioxide in baking.
Bread is made by adding water to flour, kneading the mixture to make dough and then baking it. Usually an ingredient is added to the dough to create bubbles of gas, so that the baked bread has a lighter texture (e.g. yeast).
After kneading (mixing) the dough is kept warm to encourage the yeast to respire.
Yeast can respire aerobically or anaerobically, but oxygen in the dough is soon used up so the yeast is forced to respire anaerobically.
The carbon dioxide produced by anaerobic cell respiration cannot escape from the dough and forms bubbles causing the dough to swell and rise.
Ethanol is also produced by anaerobic cell respiration, but it evaporates during baking.

54. 2.8.A1 Use of anaerobic cell respiration in yeasts to produce ethanol and carbon dioxide in baking.
Bioethanol (ethanol produced by organisms) is a renewable energy source.
Most bioethanol is produced from sugar cane and maize, using yeast.
Starch and cellulose in the plant material are broken down by enzymes into sugars.
Fermenters are used to keep the yeast in optimum conditions.
When yeast carry out anaerobic respiration the sugars in the plant material are converted to ethanol and carbon dioxide.
The ethanol produced by the yeasts is purified by distillation and water is removed to improve combustion.

55. 2.8.A2 Lactate production in humans when anaerobic respiration is used to maximize the power of muscle contractions.
Certain human activities require anaerobic respiration such as weightlifting and sprinting.
Aerobic respiration generates a much greater yield of ATP, but anaerobic respiration can supply ATP very rapidly, as oxygen is not required.
Rapid generation of ATP enables us to maximise the power of muscle contractions.
Anaerobic cell respiration produces lactate. There is a limit to the concentration that the body can tolerate and this limits how much or how long anaerobic respiration can be done for.
Afterwards lactate must be broken down. This involves the use of oxygen. It can take several minutes for enough oxygen to be absorbed for all lactate to be broken down. The demand for oxygen that builds up during a period of anaerobic respiration is called the oxygen debt.

56. Bibliography / Acknowledgments
Jason de Nys