8 - Energy Production and Metabolism

Abstract

This chapter explains that all living organisms require energy, which is obtained from the sun and the food that is ingested. The food that is consumed is degraded in the digestive tract into smaller components by the action of specific protein molecules known as enzymes. Enzymes are proteins that catalyze specific reactions, primarily by reducing the energy required for the reactants to reach their transition state. Analysis of enzyme activity is studied through enzyme kinetics that measures the rate at which enzymes catalyze reactions. Inhibitors of enzyme reactions act either by blocking the substrate from binding to the enzyme, in a process known as competitive inhibition, or by altering the activity of the enzyme without affecting substrate binding, via noncompetitive inhibition. Regulated enzymes display a complex kinetic picture, which is best characterized by sigmoidal kinetics. Regulators either increase or decrease the level of substrate required to reach maximal velocity. The chapter also discusses that metabolism is the study of chemical conversions to generate energy. It is important to regulate the metabolic pathways so that futile cycles are not maintained and required tissue specific tasks are accomplished. Multiple levels of regulation are evident and include regulation of gene transcription, allosteric regulation of enzyme activity, and covalent modification of specific enzymes.