Exam 6: Energy and Life

The ΔG of ATP hydrolysis in a test tube under standard conditions is -7.3 kcal/mol. The ΔG for the reaction A+B C under the same conditions is +4.0 kcal/mol. How would the addition of an enzyme that catalyzes A+B C most likely alter the coupled reactions?

Use the following information to answer the question below. The figure illustrates the energy states associated with the reaction A + B ↔ C + D. Which of the following terms best describe the forward reaction in the figure?

Which of the following statements best describes a system at chemical equilibrium?

Use the following information to answer the question below. Activity of various enzymes at various temperatures (A) and at various pH (b) Which temperature and pH profile curves on the graphs are most likely associated with an enzyme isolated from a human stomach where conditions are strongly acidic?

Which of the following statements best summarizes how the ATP cycle illustrated in the accompanying figure functions in cells?

Choose the pair of terms that correctly completes this sentence: Catabolism is to anabolism as ________ is to ________.

In the citric acid cycle, succinate dehydrogenase catalyzes the conversion of succinate to fumarate. This reaction is inhibited by malonate, which resembles succinate but cannot be acted upon by succinate dehydrogenase. Increasing the ratio of succinate molecules to those of malonate in the reaction reduces the inhibitory effect of malonate. What role does malonate play with respect to succinate dehydrogenase?

Which of the following statements best describes catabolic pathways?

The ΔG of ATP hydrolysis in a test tube under standard conditions is -7.3 kcal/mol. The ΔG for the reaction A + B = C under the same conditions is +4.0 kcal/mol. What is the overall free-energy change for the coupled reactions under these conditions?

Which of the following statements best describes the first law of thermodynamics?

Most cells cannot harness heat to perform work because

Which of the following statements best describes the central role that ATP plays in cellular metabolism?

A series of enzymes catalyze the reactions in the metabolic pathway X → Y → Z → A. Product A binds to the enzyme that converts X to Y at a position remote from its active site. This binding decreases the activity of the enzyme. What does substance X represent in this pathway?

Use the following information to answer the question below. The figure illustrates the energy states associated with the reaction A + B ↔ C + D. Which of the lower-case letters represents the activation energy required for the non-enzyme-catalyzed reaction in the figure?

Which of the following statements is consistent with the second law of thermodynamics?

Catalase is an enzyme that functions in human liver cells where the pH is approximately neutral. Which of the following graphs best reflects the activity profile of catalase from pH 5 to pH 9?

Which of the following terms best describes a chemical reaction for which ΔG is positive?

Which of the following statements best describes an exergonic reaction?

Disruption of the active site of an enzyme would most likely result in which of the following?

A change of a single amino acid at a position distant from the active site of an enzyme can alter the substrate specificity by changing the ________.