E3-Study Questions - Chapter 6: Energy, Enzymes, and...

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Chapter 6: Energy, Enzymes, and Metabolism KEY CONCEPTS 1. Energy is the capacity to do work. Energy occurs in two forms: potential and kinetic. 2. The first law of thermodynamics states that energy cannot be created or destroyed. The second law of thermodynamics states that, when energy is converted from one form to another, some of that energy becomes unavailable to do work. 3. Changes in free energy, total energy, temperature, and entropy are related by the equation Δ G = Δ H T Δ S . 4. Exergonic reactions have a negative Δ G, and endergonic reactions have a positive Δ G . 5. The change in free energy of a reaction determines its point of chemical equilibrium, at which the forward and reverse reactions proceed at the same rate. 6. ATP (adenosine triphosphate) serves as an energy currency in cells. The ATP cycle couples exergonic and endergonic reactions. 7. The rate of a chemical reaction is independent of G but is determined by the size of the activation energy barrier. Catalysts speed reactions by lowering the activation energy barrier. 8. Enzymes are biological catalysts, proteins that are highly specific for their substrates. 9. An enzyme’s active site determines its specificity. At the active site, a molecule of substrate can be oriented correctly, chemically modified, or strained. Also, upon binding to a substrate, some enzymes change shape, facilitating the reaction. 10. Substrate concentration affects the rate of an enzyme-catalyzed reaction. 11. Some enzymes require cofactors, coenzymes, or prosthetic groups in order to facilitate a reaction. 12. Metabolism is organized into pathways, in which the product of one reaction is a reactant for the next reaction. Each reaction is catalyzed by an enzyme. 13. The new field of systems biology studies the complex interactions of metabolic pathways. 14. Enzyme activity is subject to regulation from irreversible and reversible inhibitors. 15. Unlike enzymes with single subunits, the activity of allosteric enzymes results from the activity of both positive and negative regulators. A plot of reaction rate versus substrate concentration for allosteric enzymes results in a sigmoid curve. 16. The end product of a metabolic pathway may inhibit the allosteric enzyme that catalyzes the commitment step of the pathway. 17. Enzymes are sensitive to their environment. Both pH and temperature affect enzyme activity. CHAPTER OUTLINE 6.1 What Physical Principles Underlie Biological Energy Transformations? There are two basic types of energy and of metabolism The first law of thermodynamics: Energy is neither created nor destroyed The second law of thermodynamics: Disorder tends to increase Chemical reactions release or consume energy Chemical equilibrium and free energy are related 6.2 What Is the Role of ATP in Biochemical Energetics? ATP hydrolysis releases energy
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This test prep was uploaded on 04/09/2008 for the course BIO 140 taught by Professor Morvaridsoltani-bejnood during the Spring '08 term at University of Tennessee.

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E3-Study Questions - Chapter 6: Energy, Enzymes, and...

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