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

Increase the concentration of reactants relative to products.

Question 3

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

Accepted Answer

$$\Delta G^0$' = -RT \ln K_{eq}$$

Question 4

A reaction in a cell is described as exergonic. What does this mean about its free energy change?

Accepted Answer

$$\Delta G is $$negative, and the reaction releases energy.

Question 5

Which of the following best explains the concept of 'steady state' in cellular reactions?

Accepted Answer

Reactant and product concentrations remain constant over time, but the system is not at equilibrium.

Question 6

If a reaction has a positive $$\Delta G'$$ value, which of the following is NOT a way to make it proceed in the cell?

Accepted Answer

Increase the concentration of products relative to reactants.

Question 7

Which of the following types of cellular work is NOT directly powered by ATP hydrolysis?

Accepted Answer

Passive diffusion of molecules across the membrane.

Question 8

A reaction proceeds spontaneously in the direction that:

Accepted Answer

Increases the entropy of the universe and decreases the free energy of the system.

Question 9

Which equation (from the study materials) would you use to calculate the actual free energy change ($$\Delta G) $$for a reaction under cellular conditions?

Accepted Answer

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

Question 10

A cereal box lists 'Calories' per serving. How does this relate to the scientific definition of a calorie?

Accepted Answer

The 'Calorie' on the box is actually a kilocalorie, equal to 1000 scientific calories.

Question 11

Which of the following statements about $$\Delta G'$$ and $$\Delta G^0$' is $$correct?

Accepted Answer

$$\Delta G^0$' is $$the standard free energy change at pH 7, while $$\Delta G' is $$the actual free energy change under cellular conditions.

Question 12

A cell couples the hydrolysis of ATP ($$\Delta G^0$' = -7.3$$ kcal/mol) to a reaction with $$\Delta G^0$' = +5$$ kcal/mol. What is the net $$\Delta G^0$'$$ for the coupled reaction?

Accepted Answer

$$-2.3$$ kcal/mol

Question 13

Which of the following is a real-life example of an endergonic reaction in cells?

Accepted Answer

Synthesis of glucose from CO$$_2$$ and H$$_2O $$during photosynthesis.

Question 14

If a reaction is at equilibrium, what is the value of $$\Delta G$$?

Accepted Answer

$$\Delta G = 0$$

Question 15

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

Accepted Answer

Energy enters as sunlight, is converted by photosynthesis, and eventually dissipates as heat.

Question 16

A scientist measures the concentrations of reactants and products in a cell and finds that $$\Delta G is $$negative. What does this indicate about the reaction?

Accepted Answer

The reaction will proceed spontaneously in the forward direction.

Question 17

Which of the following is NOT a consequence of the second law of thermodynamics in biological systems?

Accepted Answer

Energy transformations are 100% efficient in cells.

Question 18

A reaction has $$\Delta G^0$' = -3$$ kcal/mol, but in the cell, the product concentration is much higher than the reactant concentration. What is likely true about $$\Delta G$$?

Accepted Answer

$$\Delta G$$ may be positive, making the reaction non-spontaneous under cellular conditions.

Question 19

Which of the following equations (from the study materials) would you use to determine the direction a reaction will proceed to reach equilibrium?

Accepted Answer

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

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

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