Q: A reaction has the following concentrations at equilibrium: $$[A] = 0.2 M$$, $$[B] = 0.2 M$$, $$[C] = 0.4 M$$, $$[D] = 0.4 M. $$What is the equilibrium constant ($$K_{eq}) $$for the reaction $$A + B \rightleftharpoons C + D$$?

$$K_{eq} = \frac{[C][D]}{[A][B]} = \frac{0.4 \times 0.4}{0.2 \times 0.2} = 4$$

Question 1

Which of the following best describes the difference between catabolic and anabolic pathways in cellular metabolism?

Accepted Answer

Catabolic pathways break down complex molecules to release energy, while anabolic pathways use energy to build complex molecules.

Question 2

According to the second law of thermodynamics, which of the following statements is true regarding entropy in biological systems?

Accepted Answer

Cells maintain order internally, but the total entropy of the universe still increases.

Question 3

A chemical reaction has a negative change in free energy ($$\Delta G \u003c 0). $$What does this indicate about the reaction?

Accepted Answer

The reaction is exergonic and can occur spontaneously.

Question 4

Which equation correctly relates the standard free energy change ($$\Delta G^\circ) to $$the equilibrium constant ($$K_{eq}$$)?

Accepted Answer

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

Question 5

A reaction has the following concentrations at equilibrium: $$[A] = 0.2 M$$, $$[B] = 0.2 M$$, $$[C] = 0.4 M$$, $$[D] = 0.4 M. $$What is the equilibrium constant ($$K_{eq}) $$for the reaction $$A + B \rightleftharpoons C + D$$?

Accepted Answer

$$K_{eq} = \frac{[C][D]}{[A][B]} = \frac{0.4 	imes 0.4}{0.2 	imes 0.2} = 4$$

Question 6

Which of the following factors does NOT affect the value of $$\Delta G$$ for a reaction?

Accepted Answer

The color of the reactants

Question 7

If a cell needs to drive an endergonic reaction ($$\Delta G \u003e 0$$), which strategy could it use to make the reaction proceed?

Accepted Answer

Couple the reaction to an exergonic process or regulate reactant/product concentrations

Question 8

Which of the following best describes the relationship between $$\Delta G$$ and equilibrium?

Accepted Answer

$$\Delta G is $$zero at equilibrium

Question 9

A scientist observes that a reaction in a cell is not proceeding spontaneously. Which of the following is the most likely explanation?

Accepted Answer

The reaction has a positive $$\Delta G$$ and requires energy input

Question 10

Which of the following is an example of biological work that involves the generation of a concentration gradient?

Accepted Answer

Active transport of ions across a membrane

Question 11

Given the equation $$\Delta G = \Delta H - T \Delta S$$, which scenario would most likely result in a spontaneous reaction?

Accepted Answer

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

Question 12

Which of the following statements about equilibrium is correct?

Accepted Answer

At equilibrium, the forward and reverse reaction rates are equal.

Question 13

A reaction has $$\Delta G^\circ = +5$$ kcal/mol. Which of the following changes would make this reaction more likely to proceed spontaneously in a cell?

Accepted Answer

Increase the concentration of reactants

Question 14

Which of the following best explains why cells do not violate the second law of thermodynamics?

Accepted Answer

Cells decrease their own entropy but increase the entropy of the universe through energy dissipation.

Question 15

Which of the following is the correct formula for calculating the free energy change ($$\Delta G) $$for the reaction $$A \rightleftharpoons B$$ under non-standard conditions?

Accepted Answer

$$\Delta G = \Delta G^\circ + RT \ln \frac{[B]}{[A]}$$

Question 16

Which of the following is a real-life example of an exergonic reaction in biological systems?

Accepted Answer

Hydrolysis of ATP to ADP and inorganic phosphate

Question 17

If the ratio $$\frac{[B]}{[A]} is $$less than $$K_{eq}$$ for the reaction $$A \rightleftharpoons B$$, what will happen?

Accepted Answer

The reaction will proceed to the right to generate more B.

Question 18

Which of the following best describes the term 'free energy' (G) in biological systems?

Accepted Answer

The energy available to do work in a system

Question 19

A cell is actively transporting sodium ions out of the cytoplasm against their concentration gradient. Which type of biological work is being performed?

Accepted Answer

Concentration work

Bioenergetics: The Flow of Energy in the Cell (Chapter 5) – Study Notes

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