Question 1

Which equation best describes the change in internal energy of a closed system according to the 1st Law of Thermodynamics?

Accepted Answer

$$\Delta U = Q - W$$

Question 2

A biochemical reaction in a cell is considered spontaneous if which of the following conditions is met?

Accepted Answer

$$\Delta G \u003c 0$$

Question 3

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

Accepted Answer

ATP hydrolysis increases entropy and relieves repulsion between negative charges, and the resulting phosphate has more resonance states.

Question 4

In a biological reaction occurring in a liquid solution, why is the work term ($$W) $$often ignored in the calculation of enthalpy?

Accepted Answer

Because there is no change in reaction volume.

Question 5

Which equation relates the change in entropy ($$\Delta S) to $$heat ($$Q) $$and temperature ($$T) in $$the classical view?

Accepted Answer

$$\Delta S = Q / T$$

Question 6

A reaction in which the products have higher energy than the reactants and $$\Delta G \u003e 0 is $$best described as:

Accepted Answer

Endergonic and non-spontaneous

Question 7

Which strategy is most commonly used to drive a metabolically irreversible reaction forward in a biological pathway?

Accepted Answer

Coupling with the catabolism of high-energy molecules to decrease enthalpy ($$\Delta H)$$

Question 8

Which of the following statements about metabolic pathways is correct?

Accepted Answer

All reactions in a linear metabolic pathway must be overall exergonic.

Question 9

What is the primary biochemical target of most drugs or toxicants in a metabolic pathway?

Accepted Answer

Metabolically irreversible enzymes

Question 10

Which equation describes the relationship between standard Gibbs free energy change ($$\Delta G^\circ) $$and the equilibrium constant ($$K_{eq}$$)?

Accepted Answer

$$\Delta G^\circ = -RT \ln K_{eq}$$

Question 11

In the statistical view of entropy, which equation is used to describe entropy ($$S$$)?

Accepted Answer

$$S = k \ln(W)$$

Question 12

Which of the following best describes the role of NADH in cellular metabolism?

Accepted Answer

NADH is an electron carrier produced in catabolic processes and used in oxidative phosphorylation.

Question 13

Which of the following is TRUE regarding the difference between steady state and equilibrium in biological systems?

Accepted Answer

At steady state, the levels of intermediates are constant but the system is open and variable due to physiological conditions.

Question 14

Which of the following best describes a metabolically reversible reaction?

Accepted Answer

It is sensitive to concentration changes of substrates and products, and catalysis direction is determined by entropy ($$\Delta S).$$

Question 15

Which of the following is a correct statement about anabolism and catabolism?

Accepted Answer

Catabolism is exothermic and commonly generates ATP/NADH/NADPH.

Question 16

Which equation describes the nonstandard Gibbs free energy change ($$\Delta G) in a $$biological system?

Accepted Answer

$$\Delta G = \Delta G^\circ + RT \ln Q$$

Question 17

Which of the following is a mobile cofactor that links reactions within metabolic pathways?

Accepted Answer

ATP

Question 18

A reaction is at equilibrium when:

Accepted Answer

The forward and reverse reaction rates are equal and $$\Delta G = 0.$$

Question 19

Which of the following is NOT a feature of metabolically irreversible reactions?

Accepted Answer

They can easily run in the reverse direction under cellular conditions.

Question 20

Which of the following best describes the effect of increasing substrate concentration in a metabolically reversible reaction?

Accepted Answer

It decreases the mass-action ratio $$Q$$ and drives the reaction forward.

Thermodynamics and High-Energy Molecules in Biochemical Reactions

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