Question 1

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

Accepted Answer

The total amount of energy in the universe is constant; energy can be transferred or transformed but never created or destroyed.

Question 2

According to the Second Law of Thermodynamics, what happens to the entropy of the universe over time?

Accepted Answer

It increases as energy is transformed.

Question 3

Which of the following best explains why sucrose does not spontaneously break down into glucose and fructose in water, even though the reaction is exergonic ($$\Delta G = -29.3 kJ$$)?

Accepted Answer

The activation energy ($$E_a) $$for the reaction is too high without an enzyme.

Question 4

What is the primary role of enzymes in biochemical reactions?

Accepted Answer

They lower the activation energy ($$E_a) $$required for the reaction to proceed.

Question 5

Which of the following statements about exergonic and endergonic reactions is correct?

Accepted Answer

Exergonic reactions have $$\Delta G  0.$$

Question 6

A student heats an egg white and observes it turning from clear to opaque. This is an example of:

Accepted Answer

Protein denaturation

Question 7

Why do enzymes not violate the first law of thermodynamics?

Accepted Answer

They only lower the activation energy ($$E_a$$), not the total energy change ($$\Delta G).$$

Question 8

Which of the following best describes how ATP enables endergonic reactions to occur in cells?

Accepted Answer

ATP hydrolysis couples with endergonic reactions, providing the required energy.

Question 9

A reaction has a negative $$\Delta G$$ but does not occur spontaneously in a test tube. What is the most likely explanation?

Accepted Answer

The activation energy ($$E_a) is $$too high to be overcome without a catalyst.

Question 10

Which of the following is NOT a function of ATP in the cell?

Accepted Answer

Acting as a catalyst for biochemical reactions

Question 11

If an enzyme is exposed to a highly acidic environment, what is the most likely outcome?

Accepted Answer

The enzyme may denature, losing its functional shape.

Question 12

Which of the following best explains why cells must continually obtain energy from their surroundings?

Accepted Answer

Because the second law of thermodynamics dictates that entropy increases, so cells must input energy to maintain order.

Question 13

Which of the following is true about the structure of ATP?

Accepted Answer

It contains three phosphate groups, a ribose sugar, and an adenine base.

Question 14

A reaction in a cell has $$\Delta G \u003e 0. $$Which of the following is most likely required for this reaction to proceed?

Accepted Answer

Coupling to ATP hydrolysis

Question 15

Which of the following best describes the relationship between activation energy ($$E_a) $$and reaction rate?

Accepted Answer

A lower $$E_a$$ results in a faster reaction rate.

Question 16

Which of the following is a correct statement about enzyme specificity?

Accepted Answer

Enzymes are specific to their substrates due to their unique three-dimensional shape.

Question 17

In the digestion of sucrose, which enzyme is responsible for catalyzing its breakdown into glucose and fructose?

Accepted Answer

Sucrase

Question 18

Which of the following best describes the effect of an enzyme on the transition state of a reaction?

Accepted Answer

It lowers the energy required to reach the transition state.

Question 19

A cell is performing active transport of a solute across its membrane. Which molecule is most likely providing the energy for this process?

Accepted Answer

ATP

Question 20

Which of the following scenarios best illustrates the coupling of an exergonic and an endergonic reaction in a cell?

Accepted Answer

The hydrolysis of ATP is used to drive the synthesis of glucose from smaller molecules.

Energy and Enzymes: Thermodynamics and Biological Reactions

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