Question 1

Which of the following best describes the first law of thermodynamics as it applies to biological systems?

Accepted Answer

Energy can be transferred and transformed, but it cannot be created or destroyed.

Question 2

A cell synthesizes a protein from amino acids. Which of the following statements about this process is correct?

Accepted Answer

It is an anabolic, endergonic reaction.

Question 3

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

Accepted Answer

$$\Delta G = G_{final} - G_{initial}$$

Question 4

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

Accepted Answer

The energy released from ATP hydrolysis ($$\Delta G  0) to $$occur.

Question 5

A reaction has a $$\Delta G of$$ $$-15 kJ/$$mol. What does this indicate about the reaction?

Accepted Answer

The reaction is exergonic and spontaneous.

Question 6

Which of the following is NOT a way that enzymes lower the activation energy ($$E_a) of a $$reaction?

Accepted Answer

By increasing the free energy change ($$\Delta G) of $$the reaction.

Question 7

A patient is diagnosed with scurvy, a disease caused by vitamin C deficiency. Which of the following best explains the molecular basis of this disease?

Accepted Answer

Vitamin C is required as a coenzyme for enzymes that hydroxylate collagen, and its absence impairs connective tissue formation.

Question 8

Which of the following statements about competitive and noncompetitive enzyme inhibitors is correct?

Accepted Answer

Competitive inhibitors bind to the active site, while noncompetitive inhibitors bind to a different site and change the enzyme's shape.

Question 9

Which of the following best describes feedback inhibition in metabolic pathways?

Accepted Answer

The end product of a pathway acts as an allosteric inhibitor of an enzyme early in the pathway.

Question 10

Which of the following scenarios best illustrates the second law of thermodynamics in biological systems?

Accepted Answer

During cellular respiration, some energy from glucose is lost as heat, increasing the entropy of the surroundings.

Question 11

Which of the following is true regarding the relationship between molecular complexity and free energy?

Accepted Answer

Larger or more complex molecules generally have more free energy than smaller or less complex molecules.

Question 12

Which of the following best explains why living cells are considered 'islands of low entropy'?

Accepted Answer

Cells maintain a high degree of order internally, even as they increase the entropy of their surroundings.

Question 13

A scientist adds an enzyme to a reaction mixture that is already at equilibrium. What will happen?

Accepted Answer

There will be no net change; the enzyme cannot shift the equilibrium position.

Question 14

Which of the following is an example of an exergonic reaction in cellular metabolism?

Accepted Answer

Hydrolysis of ATP to ADP and $$P_i$$

Question 15

Which of the following best describes allosteric regulation of enzymes?

Accepted Answer

A regulatory molecule binds to a site other than the active site, causing a conformational change that affects enzyme activity.

Question 16

Which of the following statements about the hydrolysis of ATP is correct?

Accepted Answer

It is an exergonic reaction that releases energy to drive cellular work.

Question 17

Which of the following is a likely consequence if a cell's metabolic pathways were not tightly regulated?

Accepted Answer

The cell would waste chemical resources by making more products than needed.

Question 18

Which of the following best explains why enzymes are highly specific for their substrates?

Accepted Answer

The shape and chemical environment of the enzyme's active site are complementary to the substrate.

Question 19

Which of the following is true about the effect of temperature on enzyme activity?

Accepted Answer

Each enzyme has an optimal temperature at which its activity is maximal.

Question 20

Which of the following best describes the role of coenzymes in enzyme function?

Accepted Answer

Coenzymes are organic molecules that assist enzymes, often derived from vitamins.

Introduction to Metabolism: Energy and Enzymes in Biological Systems

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