Q: A reaction has $$\Delta H = -50 kJ/$$mol and $$\Delta S = -0.1 kJ/($$mol·K). At $$T = 300 K$$, what is $$\Delta G$$ for the reaction?

$$\Delta G = -50 - (300 \times -0.1) = -50 + 30 = -20 kJ/$$mol

Question 1

Which of the following best describes the main difference between phototrophs and chemotrophs?

Accepted Answer

Phototrophs use sunlight as their energy source, while chemotrophs obtain energy by oxidizing chemical bonds in molecules.

Question 2

A muscle cell contracting to move your arm is an example of which type of cellular work?

Accepted Answer

Mechanical work

Question 3

Which of the following statements about the first law of thermodynamics is correct in the context of biological systems?

Accepted Answer

Energy can be converted from one form to another but cannot be created or destroyed.

Question 4

Which equation correctly relates free energy change ($$\Delta G$$), enthalpy change ($$\Delta H$$), and entropy change ($$\Delta S) at $$temperature $$T$$?

Accepted Answer

$$\Delta G = \Delta H - T\Delta S$$

Question 5

A reaction has $$\Delta H = -50 kJ/$$mol and $$\Delta S = -0.1 kJ/($$mol·K). At $$T = 300 K$$, what is $$\Delta G$$ for the reaction?

Accepted Answer

$$\Delta G = -50 - (300 	imes -0.1) = -50 + 30 = -20 kJ/$$mol

Question 6

Which of the following best explains why living cells are considered open systems?

Accepted Answer

They exchange both energy and matter with their surroundings.

Question 7

In the context of the second law of thermodynamics, which of the following statements is true?

Accepted Answer

The entropy of the universe increases in every spontaneous process.

Question 8

A cell maintains a high concentration of potassium ions inside and a low concentration outside. This is an example of:

Accepted Answer

Concentration work

Question 9

Which of the following is a correct statement about $$\Delta G$$ and chemical equilibrium?

Accepted Answer

At equilibrium, $$\Delta G = 0.$$

Question 10

A reaction has a standard free energy change ($$\Delta G^\circ') of$$ $$+5$$ kcal/mol. What can you conclude about the equilibrium constant ($$K'_{eq}) $$for this reaction at $$25^\circC$$?

Accepted Answer

$$K'_{eq} \u003c 1$$

Question 11

Which of the following best describes the role of bioluminescence in living organisms?

Accepted Answer

It is the production of light using an energy source such as ATP or chemical oxidation.

Question 12

Which of the following is NOT a form of work that requires energy in cells?

Accepted Answer

Passive diffusion of oxygen across a membrane

Question 13

A reaction in a cell has $$\Delta G' = +3$$ kcal/mol. Which of the following is true about this reaction under cellular conditions?

Accepted Answer

It is not thermodynamically spontaneous and requires energy input.

Question 14

Which of the following best explains why heat is not a useful energy source for most cellular processes?

Accepted Answer

Most biological systems are isothermal, so heat cannot be used to do work efficiently.

Question 15

The oxidation of glucose in cells is highly exergonic. Which of the following is true about this process?

Accepted Answer

It has a negative $$\Delta G$$ and releases energy that can be used to do work.

Question 16

A cell is able to maintain a steady state far from equilibrium by:

Accepted Answer

Continuously exchanging energy and matter with its environment.

Question 17

Which of the following equations correctly relates the standard free energy change ($$\Delta G^\circ') to $$the equilibrium constant ($$K'_{eq}) at$$ $$25^\circC$$?

Accepted Answer

$$\Delta G^\circ' = -RT \ln K'_{eq}$$

Question 18

In a red blood cell, the concentration of glucose-6-phosphate is 83 μM and fructose-6-phosphate is 14 μM. If the equilibrium constant ($$K_{eq}) $$for their interconversion is 0.5, in which direction will the reaction proceed?

Accepted Answer

Toward fructose-6-phosphate formation

Question 19

Which of the following is a correct statement about the relationship between $$\Delta G^\circ'$$ and $$K'_{eq}$$?

Accepted Answer

If $$K'_{eq} \u003e 1$$, then $$\Delta G^\circ' is $$negative.

Question 20

Which of the following best explains why a cell at equilibrium is considered dead?

Accepted Answer

No net flow of matter or energy occurs, so essential life processes cease.

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

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