Bch 3025 Exam 3 Questions With
Correct Answers
If the G'° of the reaction A -> B is -40 kJ/mol, under standard conditions the reaction:
A) is at equilibrium.
B) will never reach equilibrium.
C) will not occur spontaneously.
D) will proceed at a rapid rate.
E) will proceed spontaneously f...
EXAM STUDY MATERIALS July 26, 2024 9:30 AM Bch 3025 E xam 3 Questions With Correct Answers If the G'° of the reaction A -> B is -40 kJ/mol, under standard conditions the reaction: A) is at equilibrium. B) will never reach equilibrium. C) will not occur spontaneously. D) will proceed at a rapid rate. E) will proceed spontaneously from left to right. - answer✔✔E) will proceed spontaneously from left to right. For the reaction A - B,G'° = -60 kJ/mol. The reaction is started with 10 mmol of A; no B is initially present. After 24 hours, analysis reveals the presence of 2 mmol of B, 8 mmol of A. Which is the most likely explanation? A) A and B have reached equilibrium concentrations. B) An enzyme has shifted the equilibrium toward A. C) B formation is kinetically slow; equilibrium has not been reached by 24 hours. D) Formation of B is thermodynamically unfavorable. E) The result described is impossible, given the fact thatG'° is -60 kJ/mol. - answer✔✔C) B formation is kinetically slow; equilibrium has not been reached by 24 hours. When a mixture of 3 -phosphoglycerate and 2 -phosphoglycerate is incubated at 25°C with phosphoglycerate mutase until equilibrium is reached, the final mixtu re contains six times as much 2 -phosphoglycerate as 3 -phosphoglycerate. Which one of the following statements is most nearly correct, when applied to the reaction as written? (R = 8.315 J/mol·K; T = 298 K) 3-Phosphoglycerate 2 -phosphoglycerate A) delta G'° is -4.44 kJ/mol. EXAM STUDY MATERIALS July 26, 2024 9:30 AM B) G'° is zero. C) G'° is +12.7 kJ/mol. D) G'° is incalculably large and positive. E) G'° cannot be calculated from the information given. - answer✔✔A) delta G' ° is -4.44 kJ/mol. When a mixture of glucose 6 -phosphate and fructose 6 -phosphate is incubated with the enzyme phosphohexose isomerase (which catalyzes the interconversion of these two compounds) until equilibrium is reached, the final mixture contains twice as much glucose 6 -phosphate as fructose 6-phosphate. Which one of the following statements is best applied to this reaction outlined below? (R = 8.315 J/mol·K; T = 298 K) Glucose 6 -phosphate fructose 6 -phosphate A) G'° is incalculably large and negative. B) G'° is -1.72 kJ/mol. C) G'° is zero. D) deltaG'° is +1.72 kJ/mo l. E) G'° is incalculably large and positive. - answer✔✔D) deltaG' ° is +1.72 kJ/mol. Hydrolysis of 1 M glucose 6 -phosphate catalyzed by glucose 6 -phosphatase is 99% complete at equilibrium (in other words, only 1% of the substrate remains). Which of the f ollowing statements is most nearly correct? (R = 8.315 J/mol·K; T = 298 K) A) deltaG'° = -11 kJ/mol. B) G'° = -5 kJ/mol. C) G'° = 0 kJ/mol. D) G'° = +11 kJ/mol. E) G'° cannot be determined from the information given. - answer✔✔A) deltaG' ° = -11 kJ/mol. The reaction A + B C has aG'° of -20 kJ/mol at 25°C. Starting under standard conditions, one can predict that: A) at equilibrium, the concentration of B will exceed the concentration of A. EXAM STUDY MATERIALS July 26, 2024 9:30 AM B) at equilibrium, the concentration of C will be less than the concentration of A. C) at equilibrium, the concentration of C will be much greater than the concentration of A or B. D) C will rapidly break down to A + B. E) when A and B are mixed, the reaction will proceed rapidly toward formation of C. - answer✔✔C) at equilibrium, the concentration of C will be much greater than the concentration of A or B. Which of the following compounds has the largest negative value for the standard free -energy change (deltaG'°) upon hydrolysis? A) Acetic anhydride B) Glucose 6-phosphate C) Glutamine D) Glycerol 3 -phosphate E) Lactose - answer✔✔A) Acetic anhydride For the following reaction, deltaG'° = +29.7 kJ/mol. L-Malate + NAD+ oxaloacetate + NADH + H+ The reaction as written: A) can never occur in a cell. B) can occu r in a cell only if it is coupled to another reaction for whichG'° is positive. C) can occur only in a cell in which NADH is converted to NAD+ by electron transport. D) cannot occur because of its large activation energy. E) may occur in cells at some co ncentrations of substrate and product - answer✔✔E) may occur in cells at some concentrations of substrate and product For the reaction A -> B, the Keq' is 10^4. If a reaction mixture originally contains 1 mmol of A and no B, which one of the following must be true? A) At equilibrium, there will be far more B than A. B) The rate of the reaction is very slow. C) The reaction requires coupling to an exergonic reaction in order to proceed. EXAM STUDY MATERIALS July 26, 2024 9:30 AM D) The reaction will proceed toward B at a very high rate. E) G'° for the reaction will be large and positive. - answer✔✔A) At equilibrium, there will be far more B than A. During glycolysis, glucose 1 -phosphate is converted to fructose 6 -phosphate in two successive reactions: Glucose 1 -phosphate -> glucose 6 -phosp hate delta G'° = -7.1 kJ/mol Glucose 6 -phosphate -> fructose 6 -phosphate delta G'° = +1.7 kJ/mol delta G'° for the overall reaction is: A) -8.8 kJ/mol. B) -7.1 kJ/mol. C) -5.4 kJ/mol. D) +5.4 kJ/mol. E) +8.8 kJ/mol. - answer✔✔C) -5.4 kJ/mol. The st andard free -energy changes for the reactions below are given. Phosphocreatine -> creatine + Pi delta G'° = -43.0 kJ/mol ATP -> ADP + Pi delta G'° = -30.5 kJ/mol What is the overallG'° for the following reaction? Phosphocreatine + ADP -> creatine + ATP A) -73.5 kJ/mol B) -12.5 kJ/mol C) +12.5 kJ/mol D) +73.5 kJ/mol
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