Question 1

Which of the following best describes the difference between an open and a closed system in the context of thermodynamics?

Accepted Answer

An open system exchanges both energy and matter with its surroundings, while a closed system exchanges only energy.

Question 2

Given the equation $$\Delta G = \Delta H - T\Delta S$$, which of the following scenarios would most likely result in a spontaneous reaction at constant temperature and pressure?

Accepted Answer

$$\Delta H  0$$

Question 3

Which statement best explains why ATP hydrolysis is often coupled to unfavorable biochemical reactions?

Accepted Answer

ATP hydrolysis releases free energy, which can be used to drive reactions with a positive $$\Delta G.$$

Question 4

A reaction has $$\Delta H = +10 kJ/$$mol and $$\Delta S = +50 J/($$mol\cdot K). At what minimum temperature (in Kelvin) will this reaction become spontaneous?

Accepted Answer

$$T \u003e 200 K$$

Question 5

Which of the following best describes an entropy-driven process?

Accepted Answer

$$\Delta S is $$positive and $$\Delta G is $$negative

Question 6

Which of the following is true for a reaction at equilibrium?

Accepted Answer

$$\Delta G \approx 0$$

Question 7

A biochemical reaction has $$\Delta G'^{\circ} = +3.0 kJ/$$mol. Which of the following statements is correct?

Accepted Answer

The reaction is not favorable under standard conditions but may proceed in the cell if coupled to a favorable reaction.

Question 8

Which of the following best explains why the hydrolysis of phosphoanhydride bonds in ATP is highly exergonic?

Accepted Answer

The products of hydrolysis are more stable due to increased resonance stabilization and solvation.

Question 9

Which of the following is an example of a coupled reaction in cellular metabolism?

Accepted Answer

Glucose phosphorylation by hexokinase using ATP hydrolysis to drive the reaction.

Question 10

If a reaction has $$\Delta G \gg 0$$, which of the following is most likely true?

Accepted Answer

The reaction is not favorable in the forward direction and will require coupling to a favorable reaction to proceed.

Question 11

Which of the following best describes the role of the surroundings in the First Law of Thermodynamics as it applies to biological systems?

Accepted Answer

Energy lost from the system is absorbed by the surroundings.

Question 12

Which of the following statements about the Second Law of Thermodynamics is correct in the context of biochemistry?

Accepted Answer

The entropy of an isolated system will tend to increase to a maximum value.

Question 13

A reaction has $$\Delta H = -40 kJ/$$mol and $$\Delta S = -100 J/($$mol\cdot K). At what temperature (in Kelvin) does the reaction become non-spontaneous?

Accepted Answer

$$T \u003e 400 K$$

Question 14

Which of the following is NOT a typical characteristic of a co-substrate in biochemical reactions?

Accepted Answer

It is permanently bound to the enzyme.

Question 15

Which of the following best describes an enthalpy-driven process?

Accepted Answer

$$\Delta H is $$negative and $$\Delta S is $$negative

Question 16

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

Accepted Answer

A reaction can be spontaneous if the enthalpy decrease outweighs the entropy decrease at a given temperature.

Question 17

Which of the following is a real-life example of a reaction that is made favorable by coupling to ATP hydrolysis?

Accepted Answer

The phosphorylation of glucose to glucose-6-phosphate in glycolysis.

Question 18

Which of the following best explains why the hydrolysis of ATP is used as a universal energy currency in cells?

Accepted Answer

ATP hydrolysis releases a large amount of free energy due to the instability of its phosphoanhydride bonds.

Question 19

Which of the following statements about the coupling of reactions is correct?

Accepted Answer

A non-spontaneous reaction can proceed if it is coupled to a highly exergonic reaction such as ATP hydrolysis.

Thermodynamics and Free Energy in Biochemical Reactions

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