Cell respiration

Nature of science:

Paradigm shift—the chemiosmotic theory led to a paradigm shift in the field of bioenergetics. (2.3)

• 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.
• 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.

• 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

• 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.