Chapter 8: An Introduction to Metabolism


1 .       The process of cellular respiration, which converts simple sugars such as glucose into CO2 and water, is an example of _____. (Concept 8.1E-Book) [Hint]

 a catabolic pathway
 an energy-releasing pathway
 a pathway in which the entropy of the system increases
 The first and second choices are correct.
 The first, second, and third choices are correct.

2 .       Energy is observed in two basic forms: potential and kinetic. Which of the following correctly matches these forms with a source of energy? (Concept 8.1E-Book) [Hint]

 the motion of individual molecules—potential energy
 the heat released from a living organism—potential energy
 the energy related to the height of a bird above the ground—kinetic energy
 the covalent bonds of a sugar molecule—potential energy
 the energy associated with a gradient of ions across a membrane—kinetic energy

3 .       Which of the following statements about the combustion of glucose with oxygen to form water and carbon dioxide (C6H12O6 + 6 O2 → 6 CO2 + 6 H2O) is incorrect? (Concept 8.2E-Book) [Hint]

 This reaction is spontaneous with the release of free energy.
 The entropy of the products is greater than the entropy of the reactants.
 The free energy lost in this combustion is greater than the energy that appears as heat.
 The entropy of the universe increases as the result of this reaction.
 The reverse reaction, making glucose from water and carbon dioxide, must be an endergonic reaction.

4 .       Which of the following statements about equilibrium of chemical reactions is correct? (Concept 8.3E-Book) [Hint]

 Reactions can only go in the direction toward equilibrium.
 Most reactions in a living cell are close to equilibrium.
 A reaction that is at equilibrium is not capable of doing any work.
 The equilibrium point of a reaction represents the least stable configuration for that reaction.
 None of the statements above correctly describes some aspect of equilibrium.

5 .       Which of the following statements about ATP (adenosine triphosphate) is incorrect? (Concept 8.3E-Book) [Hint]

 The hydrolysis of ATP is an endergonic process that can supply needed energy for anabolic pathways.
 The cycling between ATP and ADP + Pi provides an energy coupling between catabolic and anabolic pathways.
 The energy release on hydrolysis of ATP is the result of breaking a high-energy bond.
 Much of the free energy released on the hydrolysis of ATP is available to do cellular work.
 In many cases, ATP makes energy available to other reactions by transferring its phosphate group to the substrate for another energy-requiring reaction.

6 .       Enzymes are described as catalysts, which means that they _____. (Concept 8.4E-Book) [Hint]

 are proteins
 provide activation energy for the reactions they facilitate
 increase the rate of a reaction without being consumed by the reaction
 can alter the free energy change (ΔG) for a chemical reaction
 increase the free energy of the reactants in order to make the reaction go faster

7 .       Which of the following would be unlikely to contribute to the substrate specificity of an enzyme? (Concept 8.4E-Book) [Hint]

 A similar shape exists between a pocket on the surface of the enzyme and a functional group on the substrate.
 The free energy of the enzyme is greater than the free energy of the substrate, which attracts the substrate to the enzyme.
 A positive charge on the substrate is attracted to a negative charge in the active site of the enzyme.
 The enzyme has the ability to change its configuration in response to the substrate binding.
 A hydrophobic group on the substrate interacts with several hydrophobic amino acids on the enzyme.

8 .       Which of the following is not a way in which an enzyme can speed up the reaction that it catalyzes? (Concept 8.4E-Book) [Hint]

 The active site can provide heat from the environment that raises the energy content of the substrate.
 Binding of the substrate to the active site can stretch bonds in the substrate that need to be broken.
 The active site of the enzyme can provide a microenvironment with a different pH that facilitates the reaction.
 The binding of two substrates in the active site provides the correct orientation for them to react to form a product.
 All of the above are ways that enzymes can speed up the rate of a chemical reaction.

9 .       The binding of a compound to an enzyme is observed to slow down or stop the rate of the reaction catalyzed by the enzyme. Which of the following could account for this observation? (Concept 8.4E-Book) [Hint]

 The compound is a competitive inhibitor.
 The compound is a negative allosteric regulator.
 The compound causes a cofactor to be lost from the enzyme.
 The first and second choices are correct.
 The first three choices are correct.

10 .       Which of the following statements about feedback regulation of a metabolic pathway is incorrect? (Concept 8.5E-Book) [Hint]

 The final product of a metabolic pathway is the compound that regulates the pathway.
 The products of the pathway become the reactants for a different reaction, and thus products are unable to accumulate.
 The enzyme that is regulated by feedback inhibition is usually the first enzyme in the metabolic pathway.
 The compound that regulates the pathway acts as a non-competitive inhibitor or a negative allosteric regulator.
 Accumulation of the product of the pathway will tend to slow down further formation of that product.

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