Question 1

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

Accepted Answer

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

Question 2

What does the Second Law of Thermodynamics imply about the fate of energy in biological reactions?

Accepted Answer

Some energy is always lost as heat, increasing entropy.

Question 3

Which equation correctly represents the change in free energy ($$\Delta G) $$for a chemical reaction?

Accepted Answer

$$\Delta G = G_{products} - G_{reactants}$$

Question 4

A reaction has $$\Delta G = -20 kJ/$$mol. Which of the following is true about this reaction?

Accepted Answer

It is exergonic and occurs spontaneously.

Question 5

Which of the following best describes the role of enzymes in chemical reactions?

Accepted Answer

Enzymes lower the activation energy ($$E_A) $$required to start a reaction.

Question 6

Which of the following reactions is most likely to be exergonic?

Accepted Answer

Hydrolysis of ATP to ADP and inorganic phosphate.

Question 7

Why are exergonic reactions considered spontaneous?

Accepted Answer

They release free energy, making $$\Delta G$$ negative.

Question 8

Which statement about activation energy ($$E_A) is $$correct?

Accepted Answer

It is the minimum energy required to start a chemical reaction.

Question 9

In a metabolic pathway, an exergonic reaction is coupled to an endergonic reaction. What is the purpose of this coupling?

Accepted Answer

To use the energy released from the exergonic reaction to drive the endergonic reaction.

Question 10

Which molecule is the primary energy currency of the cell, used to power endergonic reactions?

Accepted Answer

ATP (Adenosine Triphosphate)

Question 11

What happens to the entropy of a closed system according to the Second Law of Thermodynamics?

Accepted Answer

Entropy increases over time.

Question 12

Which of the following best describes an endergonic reaction?

Accepted Answer

It requires energy input and has a positive $$\Delta G.$$

Question 13

Which process is an example of oxidation in biological systems?

Accepted Answer

A molecule loses electrons.

Question 14

During cellular respiration, which molecule acts as the reducing agent?

Accepted Answer

The molecule that loses electrons.

Question 15

Which of the following is true about enzymes and the thermodynamics of a reaction?

Accepted Answer

Enzymes do not affect the value or sign of $$\Delta G.$$

Question 16

A scientist measures the energy released from the hydrolysis of ATP. Which value is closest to the standard free energy change ($$\Delta G) $$for this reaction?

Accepted Answer

$$-7.3 kJ/$$mol

Question 17

Which of the following scenarios best illustrates the concept of entropy in a biological system?

Accepted Answer

A drop of dye disperses evenly in a beaker of water.

Question 18

Which statement about the coupling of oxidation and reduction reactions is correct?

Accepted Answer

Oxidation and reduction are always coupled; one molecule loses electrons while another gains them.

Question 19

Which of the following is a consequence of the Second Law of Thermodynamics in living organisms?

Accepted Answer

Some energy is always lost as heat during metabolic processes.

Question 20

Which of the following best explains why enzymes are necessary for life?

Accepted Answer

They lower the activation energy, allowing reactions to occur at biological temperatures.

Energy, Thermodynamics, and Chemical Reactions in Biology

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