Question 1

Which of the following best describes the difference between catabolic and anabolic pathways in cellular metabolism?

Accepted Answer

Catabolic pathways break down complex molecules into simpler ones and release energy, while anabolic pathways build complex molecules from simpler ones and require energy.

Question 2

A scientist measures the free energy of reactants in a chemical reaction as $$G_{reactants} = 50\ \mathrm{kJ/mol}$$ and the free energy of products as $$G_{products} = 30\ \mathrm{kJ/mol}. $$What is the free energy change $$(\Delta G)$$ for this reaction, and is it spontaneous?

Accepted Answer

$$\Delta G = -20\ \mathrm{kJ/mol}$$; the reaction is spontaneous.

Question 3

Which of the following is an example of kinetic energy in a biological system?

Accepted Answer

A muscle contracting to move a limb.

Question 4

According to the Second Law of Thermodynamics, which of the following statements is correct?

Accepted Answer

Every energy transfer increases the entropy $$(S) of $$the universe.

Question 5

Which of the following best describes the structure of ATP and the biological macromolecule it most closely resembles?

Accepted Answer

ATP consists of a ribose sugar, three phosphate groups, and a nitrogenous base, making it most similar to a nucleotide.

Question 6

Which of the following is NOT a direct product of ATP hydrolysis?

Accepted Answer

Glucose

Question 7

Which of the following types of cellular work is powered by ATP and involves the movement of substances across membranes against their concentration gradient?

Accepted Answer

Transport work

Question 8

During the ATP-ADP cycle, which process is coupled to an exergonic reaction and which to an endergonic reaction?

Accepted Answer

ATP synthesis is coupled to exergonic reactions; ATP hydrolysis is coupled to endergonic reactions.

Question 9

Which of the following statements about enzymes is correct?

Accepted Answer

Enzymes lower the activation energy $$(E_a) of a $$reaction without being consumed.

Question 10

A patient is diagnosed with a genetic disorder that prevents the production of a necessary cofactor for a key metabolic enzyme. What is the most likely consequence for the enzyme's activity?

Accepted Answer

The enzyme's activity will decrease or stop because the cofactor is required for its function.

Question 11

Which of the following best describes the difference between competitive and noncompetitive enzyme inhibition?

Accepted Answer

Competitive inhibitors bind to the active site, while noncompetitive inhibitors bind to a different site on the enzyme.

Question 12

Which of the following environmental changes is most likely to increase the rate of an enzyme-catalyzed reaction up to a point, but then cause the rate to decrease if the change continues?

Accepted Answer

Raising the temperature beyond the enzyme's optimal range.

Question 13

A metabolic pathway is regulated by feedback inhibition. Which of the following best describes this process?

Accepted Answer

The final product of the pathway inhibits an enzyme that acts early in the pathway.

Question 14

Which of the following statements about allosteric enzymes is correct?

Accepted Answer

Allosteric enzymes can be regulated by molecules binding at sites other than the active site, changing the enzyme's activity.

Question 15

Which of the following best describes the relationship between exergonic and endergonic reactions in cellular metabolism?

Accepted Answer

Exergonic reactions release energy and can drive endergonic reactions through energy coupling.

Question 16

A graph shows the free energy of a reaction with and without an enzyme. The activation energy without the enzyme is $$80\ \mathrm{kJ/mol}$$, and with the enzyme is $$30\ \mathrm{kJ/mol}. $$The free energy change $$(\Delta G) is$$ $$-10\ \mathrm{kJ/mol}. $$Which of the following is true?

Accepted Answer

The enzyme decreases the activation energy but does not change the free energy change.

Question 17

Which of the following is an example of chemical work powered by ATP in a cell?

Accepted Answer

Synthesizing a polypeptide from amino acids.

Question 18

Which of the following best describes the concept of entropy $$(S) in $$biological systems?

Accepted Answer

Entropy is a measure of disorder or randomness in a system.

Question 19

Which of the following scenarios best illustrates the First Law of Thermodynamics in a biological context?

Accepted Answer

A plant converts sunlight into chemical energy during photosynthesis, but the total energy in the system and surroundings remains constant.

Energy, Enzymes, and Metabolism: Study Guide

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