Essential idea: Energy is converted to a usable form in cell respiration.
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 carbohydrates, lipids (and sometimes proteins) provide more stable longer term storage for energy. The purpose of cell respiration therefore it to breakdown carbohydrates and lipids so that ATP can be produced from ADP when needed. The image to the above to the right shows the conversion of ADP and a phosphate into ATP.
ATP can be made by substrate level phosphorylation, but most commonly oxidative phosphorylation is used. The key component in oxidative phosphorylation is ATP synthase (above left). 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.
ATP can be made by substrate level phosphorylation, but most commonly oxidative phosphorylation is used. The key component in oxidative phosphorylation is ATP synthase (above left). 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.
Understandings, applications and skills
| 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. |
| 8.2.U4 | Glycolysis gives a small net gain of ATP without the use of oxygen. [The names of the intermediate compounds in gylcolysis is not required.] |
| 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. |
| 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. |
[Text in square brackets indicates guidance notes]
Starter
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A playlist of musical summaries of the three key metabolic process involved in cell respiration by Mr W. Could you write your own one for the link reaction?
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Below are the notes for this topic. Alternatively the 8.2 Cell respiration (AHL) notes - bottom line template can be used as a note construction template in itself or as a checklist if you are using your own or another template such as the Cornell style template.
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Weblinks
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Cell Respiration
Cellular respiration by PH School Cellular respiration by Sunamas Inc. Cellular respiration a 3D animation by McGraw and Hill Cellular respiration by Handwritten tutorials (below) Glycolysis
Glycolysis by Smith University How glycolysis works by McGraw and Hill Glycolysis and fermentation in yeast by Indiana Uni has more detail than needed, but nicely illustrates that glycolysis is a metabolic pathway Glycolysis by IUBMB again contains more detail than needed, but does neatly show the bond breaking and forming Glycolysis by John Kyrk contains more detail than needed, but is a nice animation Glycolysis by Cornell University Glycolysis by National Louis University |
Krebs cycle
Citric acid cycle by National Louis University The citric acid cycle by Wiley The citric acid cycle by Interactive concepts in biochemistry How the Krebs cycle works by McGraw and Hill Krebs cycle by John Kyrk contains more detail than needed, but is a nice animation Oxidative Phosphorylation Electron transport and chemiosmosis by National Louis University Oxidative Phosphorylation by Interactive concepts in biochemistry Oxidative phosphorylation by Purdue University Electron transport system and ATP synthesis by McGraw and Hill Mitochondria/electron transport by John Kyrk contains more detail than needed, but is a nice animation |
Nature of science
Paradigm shift—the chemiosmotic theory led to a paradigm shift in the field of bioenergetics. (2.3)
To find out more about the development of chemiosmotic theory uses the links:
http://biologyjunction.com/chemiosmotic_theory.htm
http://www.nobelprize.org/nobel_prizes/chemistry/laureates/1978/press.htm
To find out more about the development of chemiosmotic theory uses the links:
http://biologyjunction.com/chemiosmotic_theory.htm
http://www.nobelprize.org/nobel_prizes/chemistry/laureates/1978/press.htm
Theory of knowledge
Peter Mitchell’s chemiosmotic theory encountered years of opposition before it was finally accepted. For what reasons does falsification not always result in an immediate acceptance of new theories or a paradigm shift?
