Question 1

Which of the following best describes the First Law of Thermodynamics as it applies to biological systems?

Accepted Answer

Energy can change forms but cannot be created or destroyed.

Question 2

A car engine burns gasoline to move the car and produces heat. According to the Second Law of Thermodynamics, what happens to the energy in this process?

Accepted Answer

Some energy is lost as heat, increasing the entropy of the universe.

Question 3

Which equation correctly represents the change in free energy for a chemical reaction?

Accepted Answer

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

Question 4

A reaction has $$\Delta H = +10 kJ/$$mol and $$\Delta S = +0.05 kJ/($$mol\cdot K).$ At what temperature (in K) does the reaction become spontaneous?

Accepted Answer

$$T \u003e 200 K$$

Question 5

Which of the following is an example of an exergonic reaction?

Accepted Answer

Breakdown of glucose during cellular respiration

Question 6

Why is heat considered the lowest grade of energy in biological systems?

Accepted Answer

Heat increases random movement and is difficult to harness for work.

Question 7

Which of the following statements about entropy ($$S) is $$correct?

Accepted Answer

Entropy is a measure of disorder and increases with every energy transformation.

Question 8

A protein folds spontaneously in water due to the hydrophobic effect. What is the main thermodynamic driving force for this process?

Accepted Answer

Increase in entropy ($$\Delta S) of $$water molecules

Question 9

Which of the following best explains why living organisms do not violate the Second Law of Thermodynamics?

Accepted Answer

Living organisms decrease entropy locally but increase entropy in the universe overall.

Question 10

Which of the following is true about ATP in cellular metabolism?

Accepted Answer

ATP stores potential energy in its phosphoanhydride bonds.

Question 11

A reaction has $$\Delta G = +15 kJ/$$mol. Which of the following statements is correct?

Accepted Answer

The reaction is non-spontaneous and requires energy input.

Question 12

Which of the following best describes energy coupling in cells?

Accepted Answer

An exergonic reaction drives an endergonic reaction.

Question 13

Which of the following is NOT a form of potential energy?

Accepted Answer

Heat energy

Question 14

If a reaction in a cell has $$\Delta H = -30 kJ/$$mol and $$\Delta S = -0.05 kJ/($$mol\cdot K),$$ at T = 300$ K, what is $$\Delta G$?

Accepted Answer

$$\Delta G = -15 kJ/$$mol

Question 15

Which of the following is an example of an anabolic pathway?

Accepted Answer

Synthesis of protein from amino acids

Question 16

Why do reactions in a closed system eventually stop doing work?

Accepted Answer

They reach equilibrium and no free energy is available for work.

Question 17

Which of the following statements about Gibbs free energy ($$G) is $$correct?

Accepted Answer

$$G is $$the energy available to do work in a system.

Question 18

Which of the following best explains why ATP hydrolysis is often coupled to endergonic reactions in cells?

Accepted Answer

ATP hydrolysis releases free energy that can drive non-spontaneous processes.

Question 19

Which of the following is a correct statement about catabolic pathways?

Accepted Answer

They release energy by breaking down complex molecules.

Question 20

Which of the following is true about the relationship between free energy and entropy in a spontaneous reaction?

Accepted Answer

Free energy decreases and entropy increases.

LEC 9: Metabolism and Energy: Thermodynamics in Biological Systems

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