An Introduction to Metabolism

1. Chapter 8 An Introduction to Metabolism Questions prepared by Jung Choi Georgia Institute of Technology

2. Living Organisms and Order The laws of thermodynamics do not apply to living organisms. Living organisms create order by using energy from the sun. Living organisms create order locally, but the energy transformations generate waste heat that increases the entropy of the universe. How do living organisms create macromolecules, organelles, cells, tissues, and complex higher-order structures?

3. Free Energy, Enthalpy, and Entropy the change in enthalpy (H) is negative. the change in enthalpy (H) is positive, but the change in entropy is greater. the reaction is endergonic, because it absorbs heat. the reaction must be coupled to an exergonic reaction. the reaction cannot occur spontaneously. When sodium chloride (table salt) crystals dissolve in water, the temperature of the solution decreases. This means that, for dissociation of Na+ and Cl– ions,

4. Life and Chemical Equilibrium yes no only the exergonic reactions all reactions except those powered by ATP hydrolysis Are most chemical reactions at equilibrium in living cells?

5. Free Energy The reaction could be coupled to power an endergonic reaction with a G of 8.8 kcal/mol. The reaction would result in a decrease in entropy (S) and an increase in the energy content (H) of the system. The reaction would result in an increase in entropy (S) and a decrease in the energy content (H) of the system. The reaction would result in products with a greater free-energy content than in the initial reactants. A reaction has a ∆G of 5.6 kcal/mol. Which of the following would most likely be true?

6. The hydrolysis of ATP: ATP  H2O → ADP  Pi is exergonic, with a G of 7.3 kcal/mol under standard conditions. What is the source of the 7.3 kcal/mol released in this reaction? breaking the terminal phosphate bond in ATP the increase in entropy from breaking apart ATP both the energy released from breaking the terminal phosphate bond and the increase in entropy the difference between the potential energy in the bonds of ATP and the water molecule, minus the potential energy in the bonds of ADP and Pi

7. Rate of a Chemical Reaction The glucose molecules lack the activation energy at room temperature. There is too much CO2 in the air. CO2 has higher energy than glucose. The formation of six CO2 molecules from one glucose molecule decreases entropy. The water molecules quench the reaction. The oxidation of glucose to CO2 and H2O is highly exergonic: G = –636 kcal/mole. Why doesn’t glucose spontaneously combust?

8. Enzymes Luciferase makes the G of the reaction more negative. Luciferase lowers the transition energy of the reaction. Luciferase alters the equilibrium point of the reaction. Luciferase makes the reaction irreversible. all of the above Firefly luciferase catalyzes the reactionluciferin  ATP ↔ adenyl-luciferin  pyrophosphatethen the next reaction occurs spontaneously:adenyl-luciferin  O2 → oxyluciferin  H2O  CO2 AMP  lightWhat is the role of luciferase?

9. Enzyme-Catalyzed Reactions a b c d e In the energy diagram below, which of the lettered energy changes would be the same in both the enzyme-catalyzed and uncatalyzed reactions?

10. This figure could represent the rate of an enzyme-catalyzed reaction facilitated diffusion active transport any of the above

11. If this is an enzyme-catalyzed reaction, how can the rate of this reaction be increased beyond the maximum velocity in this figure? Increase the substrate concentrations. Increase the amount of enzyme. Increase the amount of energy. any of the above There is no way to increase the rate of the reaction any further.

12. Enzyme Inhibitors competitive inhibitors. noncompetitive inhibitors. allosteric regulators. prosthetic groups. feedback inhibitors. Vioxx and other prescription nonsteroidal anti-inflammatory drugs (NSAIDs) are potent inhibitors of the cycloxygenase-2 (COX-2) enzyme. High substrate concentrations reduce the efficacy of inhibition by these drugs. These drugs are

13. Enzyme Regulation cooperative activation. allosteric activation. activation by an enzyme cofactor. coupling exergonic and endergonic reactions. Adenosine monophosphate (AMP) activates the enzyme phosphofructokinase (PFK) by binding at a site distinct from the substrate binding site. This is an example of

14. Which enzymes may translocate from the cytoplasm to associate with the cytoplasmic face of the plasma membrane in response to a signal? ion channels active transport proteins phospholipid hydrolases aTP synthases motor proteins