Question 1

Which of the following best explains why ATP is considered the 'energy currency' of the cell?

Accepted Answer

ATP hydrolysis releases a moderate amount of free energy, allowing it to couple both exergonic and endergonic reactions efficiently.

Question 2

Given the reaction $$\mathrm{A} + \mathrm{B} \rightleftharpoons \mathrm{C} + \mathrm{D}$$, the relationship between the standard free energy change and the equilibrium constant is:

Accepted Answer

$$\Delta G$$^{\circ\prime}$$ = -RT \ln K'_{eq}$$

Question 3

Which of the following statements about the hydrolysis of ATP is TRUE?

Accepted Answer

ATP hydrolysis is highly exergonic due to relief of charge repulsion and resonance stabilization of products.

Question 4

Which compound has the most negative standard free energy of hydrolysis according to the provided diagram?

Accepted Answer

Phosphoenolpyruvate

Question 5

A reaction has $$\Delta H  0. $$What can you conclude about $$\Delta G$$?

Accepted Answer

$$\Delta G$$ will always be negative.

Question 6

Why are steps with large negative changes in free energy ($$\Delta G) $$often key regulatory points in metabolic pathways?

Accepted Answer

They are essentially irreversible under cellular conditions, making them ideal for controlling pathway direction and flux.

Question 7

Which of the following best describes the effect of coupling ATP hydrolysis to an endergonic reaction?

Accepted Answer

It allows the overall reaction to become exergonic and proceed spontaneously.

Question 8

For the reaction $$\mathrm{E} \rightleftharpoons \mathrm{F}$$ with $$K_{eq} = 1$$, what is the value of $$\Delta G$$^{\circ\prime}$$?

Accepted Answer

$$\Delta G$$^{\circ\prime}$$ = 0$$

Question 9

Which of the following is a reason why phosphoenolpyruvate (PEP) can transfer its phosphate group to ADP to form ATP, but glucose-6-phosphate cannot?

Accepted Answer

PEP has a more negative $$\Delta G$$^{\circ\prime}$$ of hydrolysis than ATP, while glucose-6-phosphate does not.

Question 10

Which of the following mechanisms for the phosphorylation of fructose-6-phosphate (F6P) to fructose-1,6-bisphosphate (F16BP) is more biochemically feasible, and why?

Accepted Answer

Mechanism II: ATP transfers its γ phosphate directly to F6P, because direct group transfer is more efficient and commonly catalyzed by kinases.

Question 11

Which of the following best describes the role of entropy ($$\Delta S) in $$protein folding?

Accepted Answer

Protein folding is driven by an increase in entropy of the surroundings due to the hydrophobic effect.

Question 12

Which of the following is TRUE regarding the additivity of $$\Delta G$$^{\circ\prime}$$ values in coupled reactions?

Accepted Answer

The overall $$\Delta G$$^{\circ\prime}$$ for a coupled reaction is the sum of the individual $$\Delta $$G^{\circ\prime}$$ values.

Question 13

Which of the following is a correct interpretation of the equation $$\Delta G = \Delta H - T\Delta S$$?

Accepted Answer

A reaction is spontaneous if $$\Delta G \u003c 0.$$

Question 14

Which of the following is NOT a way that cells maintain flux through a metabolic pathway?

Accepted Answer

By allowing all reactions to reach equilibrium.

Question 15

In the glycolytic pathway, why is the conversion of phosphoenolpyruvate (PEP) to pyruvate coupled to ATP synthesis?

Accepted Answer

Because the hydrolysis of PEP has a highly negative $$\Delta G$$^{\circ\prime}$$, which can drive the phosphorylation of ADP to ATP.

Question 16

Which of the following statements about standard free energy change ($$\Delta G$$^{\circ\prime}$$) and cellular free energy change ($$\Delta G$$) is correct?

Accepted Answer

$$\Delta G$$ depends on actual cellular concentrations of reactants and products, while $$\Delta G$$^{\circ\prime}$$ is measured under standard conditions.

Question 17

Which of the following best explains why ATP hydrolysis can drive the phosphorylation of glucose to glucose-6-phosphate?

Accepted Answer

The overall coupled reaction has a negative $$\Delta G$$, making it spontaneous.

Question 18

Which of the following is a consequence of a reaction step in a metabolic pathway having a large negative $$\Delta G$$?

Accepted Answer

The reaction is a likely regulatory point and essentially irreversible under physiological conditions.

Bioenergetics and Metabolic Pathway Regulation: Study Notes

Study Guide - Practice Questions

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