Question 1

Which of the following best describes why cells are considered an open system in thermodynamics?

Accepted Answer

Cells exchange both energy and matter with their surroundings.

Question 2

A biochemical reaction has a standard free energy change ($$\Delta G^0$') of$$ $$+5$$ kcal/mol. Which of the following strategies could make this reaction proceed in the cell?

Accepted Answer

Couple the reaction to an exergonic reaction with a large negative $$\Delta G'$$ value.

Question 3

Which equation relates the change in free energy ($$\Delta G) to $$the equilibrium constant ($$K_{eq}) $$for a biochemical reaction?

Accepted Answer

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

Question 4

Which of the following statements about entropy and the direction of chemical reactions is correct?

Accepted Answer

Reactions proceed in the direction that increases the entropy of the universe and decreases the free energy of the system.

Question 5

A reaction in a cell has $$\Delta G' = +3$$ kcal/mol. Which of the following best describes this reaction?

Accepted Answer

It is endergonic and will not proceed spontaneously unless coupled to another reaction.

Question 6

Which term describes the condition in which cellular reactions maintain constant concentrations of reactants and products, but are not at equilibrium?

Accepted Answer

Steady state

Question 7

If a reaction has $$\Delta G^0$' = -7$$ kcal/mol, what does this indicate about the reaction under standard conditions?

Accepted Answer

The reaction is exergonic and will proceed spontaneously.

Question 8

Which of the following is the correct definition of a calorie?

Accepted Answer

The amount of energy required to raise the temperature of 1 gram of water by 1 degree Celsius.

Question 9

Which equation would you use to calculate the actual free energy change ($$\Delta G') $$for a reaction given concentrations of reactants and products?

Accepted Answer

$$\Delta G' = \Delta G^0$' + RT \ln \frac{[products]}{[reactants]}$$

Question 10

A cell needs to drive an endergonic reaction ($$\Delta G' \u003e 0). $$Which of the following is NOT a way to make the reaction proceed?

Accepted Answer

Increase the concentration of products.

Question 11

Which of the following best explains the difference between $$\Delta G^0$'$$ and $$\Delta G'$$?

Accepted Answer

$$\Delta G^0$' is $$the free energy change under standard conditions, while $$\Delta G' is $$the free energy change under actual cellular conditions.

Question 12

Which of the following types of work is NOT performed by cells?

Accepted Answer

Nuclear work (e.g., nuclear fission)

Question 13

A reaction has $$\Delta G' = 0. $$What does this indicate about the reaction?

Accepted Answer

The reaction is at equilibrium.

Question 14

Which of the following best describes the linear flow of energy in the biosphere?

Accepted Answer

Energy flows in one direction, while organic molecules cycle.

Question 15

Which of the following is an example of coupling reactions in a cell?

Accepted Answer

Using ATP hydrolysis ($$\Delta G' = -7.3$$ kcal/mol) to drive glucose phosphorylation ($$\Delta G' = +3.3$$ kcal/mol).

Question 16

Which law of thermodynamics is most directly applied in bioenergetics to predict the direction of cellular reactions?

Accepted Answer

Second law: entropy of the universe must increase.

Question 17

A reaction in a cell is not at equilibrium. What does the sign of $$\Delta G'$$ indicate?

Accepted Answer

If $$\Delta G' is $$negative, the reaction will proceed spontaneously toward equilibrium.

Question 18

Which of the following is a real-life example of altering reactant/product ratios to drive a reaction?

Accepted Answer

Increasing oxygen concentration in tissues to promote cellular respiration.

Question 19

Which of the following best describes an exergonic reaction?

Accepted Answer

A reaction with $$\Delta G' \u003c 0$$ that releases energy.

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

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