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Question 1

Which of the following statements are true for the enzyme at the rate-limiting step of a metabolic pathway?

a. Concentration of its substrate is higher than its Km value
b. The measured reaction rate is close to its Vmax
c. Its Vmax is higher than that of other enzymes in the pathway
d. Its Km value is higher than that of other enzymes in the pathway
e. Its Km value is lower than that of other enzymes in the pathway

Answer 1

a. Concentration of its substrate is higher than its Km value
b. The measured reaction rate is close to its Vmax

Question 2

Which input path of a branched metabolic pathway is more relevant physiologically?

a. The one that has the highest metabolic flux in vivo
b. The one that has the enzyme with the highest Vmax
c. The one that has the enzyme with the lowest Km
d. The one that has lower number of enzymatic steps involved
e. The one that has the highest in vivo substrate concentration at the first enzymatic reaction

Answer 2

a. The one that has the highest metabolic flux in vivo

Question 3

Which of the following statements is true when the rate-limiting step of a reaction pathway is inhibited?

a. Concentration of the substrate at the inhibited enzyme drops
b. Rate of the inhibited reaction is lower than that of the others in the pathway
c. Concentration of the product at the inhibited enzyme drops
d. Concentrations of the intermediers in the pathway do not change
e. Steady-state flux of the pathway is unaltered

Answer 3

c. Concentration of the product at the inhibited enzyme drops

Question 4

Which of the following statements is true for a reaction pathway under conditions of steady-state?

a. Concentrations of intermediers are unaltered
b. Vmax values of enzymes involved are equal
c. Reaction rate at the rate-limiting step is the lowest
d. Concentrations of intermediers are equal
e. The system is in thermodynamic equilibrium

Answer 4

a. Concentrations of intermediers are unaltered

Question 5

Which conditions are necessary for two reactions to be enzymatically coupled? (Eact: activation energy)

a. Both reactions include phosphoryl transfer.
b. Eact of both reactions is high.
c. At least one of the reactions is oxidoreduction.
d. ΔG of the two reactions has different signs (one negative and one positive).
e. Eact of both reactions is low.

Answer 5

b. Eact of both reactions is high.
d. ΔG of the two reactions has different signs (one negative and one positive).

Question 6

Which conditions rule out the enzymatic coupling of two reactions? (Eact: activation energy)

a. One of the reactions has low Eact.
b. Eact of both reactions is high.
c. ΔG of both reactions is negative.
d. ΔG of the two reactions has different signs (one negative and one positive).
e. One of the reactions is oxidoreduction.

Answer 6

a. One of the reactions has low Eact.
c. ΔG of both reactions is negative.

Question 7

Which statement is true regarding the group transfer potential (gtp)? Select one or more:

a. Gtp is the absolute value of the ΔG of hydrolysis (when the group is released).
b. Functional groups have a natural tendency to move from the lower toward the higher gtp.
c. Functional groups have a natural tendency to move from the higher toward the lower gtp.
d. ΔG of a group transfer equals the gtp of the group acceptor plus the gtp of the group donor.
e. ΔG of a group transfer equals the gtp of the group acceptor minus the gtp of the group donor.

Answer 7

a. Gtp is the absolute value of the ΔG of hydrolysis (when the group is released).
c. Functional groups have a natural tendency to move from the higher toward the lower gtp.
e. ΔG of a group transfer equals the gtp of the group acceptor minus the gtp of the group donor.

Question 8

Which statement is false regarding the group transfer potential (gtp)?

Select one or more:
a. The molecule of the lowest gtp is suitable as a group carrier.
b. Functional groups have a natural tendency to move from the lower toward the higher gtp.
c. ΔG of a group transfer equals the gtp of the group donor minus the gtp of the group acceptor.
d. Low gtp means that the group is attached to the molecule with a weak bond.
e. High gtp indicates a great tendency of the molecule to accept the group.

Answer 8

All correct

Question 9

Which statement is false regarding the group transfer potential (gtp)?

Select one or more:
a. ΔG of a group transfer equals the gtp of the group acceptor plus the gtp of the group donor.
b. Functional groups have a natural tendency to move from the higher toward the lower gtp.
c. Low gtp means that the group is attached to the molecule with a weak bond.
d. High gtp indicates a great tendency of the molecule to accept the group.
e. Gtp is the absolute value of the ΔG of hydrolysis (when the group is released).

Answer 9

a. ΔG of a group transfer equals the gtp of the group acceptor plus the gtp of the group donor.
c. Low gtp means that the group is attached to the molecule with a weak bond.
d. High gtp indicates a great tendency of the molecule to accept the group.