Lecture 32 Summary

Mitochondria: structure and function.

In the electron transport chain, the free energy available from oxidation of the reducing equivalents carried by NADH or FADH₂ by oxygen to water is used to generate a transmembrane H⁺ gradient.

Chemiosmotic hypothesis (Mitchell, 1961)

ATP synthase uses the free energy of the transmembrane H⁺ gradient to drive the reaction ADP + P_i → ATP.

Other regulatory features: Hexokinase : . Pyruvate kinase: Feed-forward activation by FBP; product inhibition by ATP. cellular glucose uptake by transporters. Glycolysis vs. gluconeogenesis; Substrate cycles.

Learning objectives

• Explain the concept of redox balance and describe how the difference between aerobic and anaerobic conditions affects the fate of pyruvate generated by glycolysis.
• Define what is meant by the term committed step, and explain why it is typically subject to regulation
• Describe the regulation of phosphofructokinase, hexokinase, and pyruvate kinase.
• Explain how the roles of skeletal muscle, heart muscle, and liver relate to the regulatory properties of the corresponding isozymes of phosphofructokinase, hexokinase, and pyruvate kinase.
• Define the term metabolic flux.

Page updated 12-18-06

References

1. Staunton J. Primary Metabolism: A Mechanistic Approoach (1978, Oxford University Press)
2. Voet D, Voet JG. Biochemistry (Vol 1, 3rd ed. 2004, John Wiley & Sons)