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8.2 Cell respiration

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Description

Nature of science:
Paradigm shift—the chemiosmotic theory led to a paradigm shift in the field of bioenergetics. (2.3)
Understandings:
  • Cell respiration involves the oxidation and reduction of electron carriers.
  • Phosphorylation of molecules makes them less stable.
  • In glycolysis, glucose is converted to pyruvate in the cytoplasm.
  • Glycolysis gives a small net gain of ATP without the use of oxygen.
  • 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 the Krebs cycle, the oxidation of acetyl groups is coupled to the reduction of hydrogen carriers, liberating carbon dioxide.
  • Energy released by oxidation reactions is carried to the cristae of the mitochondria by reduced NAD and FAD.
  • Transfer of electrons between carriers in the electron transport chain in the membrane of the cristae is coupled to proton pumping.
  • Oxygen is the final electron acceptor.
  • 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.
  • The structure of the mitochondrion is adapted to the function it performs.
Applications and skills:
  • Application: Electron tomography used to produce images of active mitochondria.
  • Skill: Analysis of diagrams of the pathways of aerobic respiration to deduce where decarboxylation and oxidation reactions occur.
  • Skill: Annotation of a diagram of a mitochondrion to indicate the adaptations to its function.
Guidance:
  • The names of the intermediate compounds in gylcolysis and the Krebs cycle are not required.
 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?
Utilization:
Syllabus and cross-curricular links:
Biology
Topic 2.8 Cell respiration
Chemistry
Topic 9.1 Oxidation and reduction

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