AP Bio cell energetics

55) Which of the following represents the activation energy needed for the enzyme-catalyzed reverse reaction, C + D → A + B? A) a B) b C) c D) d E) e

A

Entropy

A measure of disorder or randomness.

endergonic reaction

A non-spontaneous chemical reaction in which free energy is absorbed from the surroundings. starts off at bottom increases and then stabilizes. 𝚫G>0 (not spontaneous)

exergonic reaction

A spontaneous chemical reaction in which there is a net release of free energy from bonds being broken. starts off on an increase and then decreases and then stabilizes. 𝚫G<0 (spontaneous)

51) How do cells use the ATP cycle shown in the figure? A) Cells use the cycle to recycle ADP and phosphate. B) Cells use the cycle to recycle energy released by ATP hydrolysis. C) Cells use the cycle to recycle ADP, phosphate, and the energy released by ATP hydrolysis. D) Cells use the cycle to generate or consume water molecules as needed. E) Cells use the cycle primarily to generate heat.

A) Cells use the cycle to recycle ADP and phosphate.

50) Which of the following is the most correct interpretation of the figure? A) Inorganic phosphate is created from organic phosphate. B) Energy from catabolism can be used directly for performing cellular work. C) ADP + ℗i are a set of molecules that store energy for catabolism. D) ATP is a molecule that acts as an intermediary to store energy for cellular work. E) ℗i acts as a shuttle molecule to move energy from ATP to ADP.

A) Inorganic phosphate is created from organic phosphate.

61) What is malonic acid's role with respect to succinate dehydrogenase? A) It is a competitive inhibitor. B) It blocks the binding of fumarate. C) It is a noncompetitive inhibitor. D) It is able to bind to succinate. E) It is an allosteric regulator.

A) It is a competitive inhibitor.

39) Some of the drugs used to treat HIV patients are competitive inhibitors of the HIV reverse transcriptase enzyme. Unfortunately, the high mutation rate of HIV means that the virus rapidly acquires mutations with amino acid changes that make them resistant to these competitive inhibitors. Where in the reverse transcriptase enzyme would such amino acid changes most likely occur in drug-resistant viruses? A) in or near the active site B) at an allosteric site C) at a cofactor binding site D) in regions of the protein that determine packaging into the virus capsid E) anywhere, with equal probability

A) in or near the active site

57) Which of these represents the activation energy required for the enzyme-catalyzed reaction? A) a B) b C) c D) d E) e

B

63) With respect to the enzyme that converts X to Y, substance A functions as A) a coenzyme. B) an allosteric inhibitor. C) the substrate. D) an intermediate. E) a competitive inhibitor.

B

31) During a laboratory experiment, you discover that an enzyme-catalyzed reaction has a ∆G of -20 kcal/mol. If you double the amount of enzyme in the reaction, what will be the ∆G for the new reaction? A) -40 kcal/mol B) -20 kcal/mol C) 0 kcal/mol D) +20 kcal/mol E) +40 kcal/mol

B) -20 kcal/mol

30) Which of the following statements regarding enzymes is true? A) Enzymes increase the rate of a reaction by making the reaction more exergonic. B) Enzymes increase the rate of a reaction by lowering the activation energy barrier. C) Enzymes increase the rate of a reaction by reducing the rate of reverse reactions. D) Enzymes change the equilibrium point of the reactions they catalyze. E) Enzymes make the rate of a reaction independent of substrate concentrations.

B) Enzymes increase the rate of a reaction by lowering the activation energy barrier.

40) Protein kinases are enzymes that transfer the terminal phosphate from ATP to an amino acid residue on the target protein. Many are located on the plasma membrane as integral membrane proteins or peripheral membrane proteins. What purpose may be served by their plasma membrane localization? A) ATP is more abundant near the plasma membrane. B) They can more readily encounter and phosphorylate other membrane proteins. C) Membrane localization lowers the activation energy of the phosphorylation reaction. D) They flip back and forth across the membrane to access target proteins on either side. E) They require phospholipids as a cofactor.

B) They can more readily encounter and phosphorylate other membrane proteins.

42) How does a noncompetitive inhibitor decrease the rate of an enzyme reaction? A) by binding at the active site of the enzyme B) by changing the shape of the enzyme's active site C) by changing the free-energy change of the reaction D) by acting as a coenzyme for the reaction E) by decreasing the activation energy of the reaction

B) by changing the shape of the enzyme's active site

52) Which of the following terms best describes the forward reaction? A) endergonic, ∆G > 0 B) exergonic, ∆G < 0 C) endergonic, ∆G < 0 D) exergonic, ∆G > 0 E) chemical equilibrium, ∆G = 0

B) exergonic, ∆G < 0

45) The mechanism in which the end product of a metabolic pathway inhibits an earlier step in the pathway is most precisely described as A) metabolic inhibition. B) feedback inhibition. C) allosteric inhibition. D) non-cooperative inhibition. E) reversible inhibition.

B) feedback inhibition.

32) The active site of an enzyme is the region that A) binds allosteric regulators of the enzyme. B) is involved in the catalytic reaction of the enzyme. C) binds noncompetitive inhibitors of the enzyme. D) is inhibited by the presence of a coenzyme or a cofactor.

B) is involved in the catalytic reaction of the enzyme.

58) Which of these represents the activation energy required for a non-catalyzed reaction? A) a B) b C) c D) d E) e

C

46) Which of the following statements describes enzyme cooperativity? A) A multi-enzyme complex contains all the enzymes of a metabolic pathway. B) A product of a pathway serves as a competitive inhibitor of an early enzyme in the pathway. C) A substrate molecule bound to an active site of one subunit promotes substrate binding to the active site of other subunits. D) Several substrate molecules can be catalyzed by the same enzyme. E) A substrate binds to an active site and inhibits cooperation between enzymes in a pathway.

C) A substrate molecule bound to an active site of one subunit promotes substrate binding to the active site of other subunits.

Succinate dehydrogenase catalyzes the conversion of succinate to fumarate. The reaction is inhibited by malonic acid, which resembles succinate but cannot be acted upon by succinate dehydrogenase. Increasing the ratio of succinate to malonic acid reduces the inhibitory effect of malonic acid. 60) Based on this information, which of the following is correct? A) Succinate dehydrogenase is the enzyme, and fumarate is the substrate. B) Succinate dehydrogenase is the enzyme, and malonic acid is the substrate. C) Succinate is the substrate, and fumarate is the product. D) Fumarate is the product, and malonic acid is a noncompetitive inhibitor. E) Malonic acid is the product, and fumarate is a competitive inhibitor.

C) Succinate is the substrate, and fumarate is the product.

A series of enzymes catalyze the reaction 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. 62) What is substance X? A) a coenzyme B) an allosteric inhibitor C) a substrate D) an intermediate E) the product

C) a substrate

44) How might an amino acid change at a site distant from the active site of the enzyme alter the enzyme's substrate specificity? A) by changing the enzyme's stability B) by changing the enzyme's location in the cell C) by changing the shape of the protein D) by changing the enzyme's pH optimum E) an amino acid change away from the active site cannot alter the enzyme's substrate specificity

C) by changing the shape of the protein

41) When you have a severe fever, what grave consequence may occur if the fever is not controlled? A) destruction of your enzymes' primary structure B) removal of amine groups from your proteins C) change in the tertiary structure of your enzymes D) removal of the amino acids in the active sites of your enzymes E) binding of your enzymes to inappropriate substrates

C) change in the tertiary structure of your enzymes

35) Increasing the substrate concentration in an enzymatic reaction could overcome which of the following? A) denaturation of the enzyme B) allosteric inhibition C) competitive inhibition D) saturation of the enzyme activity E) insufficient cofactors

C) competitive inhibition

53) Which of the following represents the ΔG of the reaction? A) a B) b C) c D) d E) e

D

54) Which of these would be the same in either an enzyme-catalyzed or a non-catalyzed reaction? A) a B) b C) c D) d E) e

D

56) Which of the following represents the difference between the free-energy content of the reactants and the free-energy content of the products? A) a B) b C) c D) d E) e

D

36) Which of the following is true of enzymes? A) Non-protein cofactors alter the substrate specificity of enzymes. B) Enzyme function is increased if the 3-D structure or conformation of an enzyme is altered. C) Enzyme function is independent of physical and chemical environmental factors such as pH and temperature. D) Enzymes increase the rate of chemical reaction by lowering activation energy barriers. E) Enzymes increase the rate of chemical reaction by providing activation energy to the

D) Enzymes increase the rate of chemical reaction by lowering activation energy barriers.

33) According to the induced fit hypothesis of enzyme catalysis, which of these is correct? A) The binding of the substrate depends on the shape of the active site. B) Some enzymes change their structure when activators bind to the enzyme. C) A competitive inhibitor can outcompete the substrate for the active site. D) The binding of the substrate changes the shape of the enzyme's active site. E) The active site creates a microenvironment ideal for the reaction.

D) The binding of the substrate changes the shape of the enzyme's active site.

47) Allosteric enzyme regulation is usually associated with A) lack of cooperativity. B) feedback inhibition. C) activating activity. D) an enzyme with more than one subunit. E) the need for cofactors.

D) an enzyme with more than one subunit.

59) Which of these represents the activation energy needed for the non-catalyzed reverse reaction, C + D → A + B? A) a B) b C) c D) d E) e

E

Enthalpy

total energy of a system