Question 1

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

Accepted Answer

Catabolic pathways break down complex molecules into simpler ones, releasing energy; anabolic pathways build complex molecules from simpler ones, requiring energy input.

Question 2

According to the First Law of Thermodynamics, which of the following statements is correct regarding energy in biological systems?

Accepted Answer

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

Question 3

A chemical reaction has a change in free energy $$\Delta G = -15\ \mathrm{kJ/mol}. $$Which of the following is true about this reaction?

Accepted Answer

The reaction is spontaneous and can perform work.

Question 4

Which of the following best explains how living organisms maintain order while increasing the entropy of the universe?

Accepted Answer

They use energy to create order locally, but in doing so, release heat and increase the entropy of their surroundings.

Question 5

Which of the following equations correctly represents the change in free energy for a chemical reaction?

Accepted Answer

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

Question 6

Which statement about ATP is correct?

Accepted Answer

ATP hydrolysis releases energy by breaking the bonds between phosphate groups, resulting in a state of lower free energy.

Question 7

A cell couples the hydrolysis of ATP ($$\Delta G = -30.5\ \mathrm{kJ/mol}) to an $$endergonic reaction with $$\Delta G = +20\ \mathrm{kJ/mol}. $$What is the overall $$\Delta G$$ for the coupled process, and is it spontaneous?

Accepted Answer

$$\Delta G = -10.5\ \mathrm{kJ/mol}$$; the process is spontaneous.

Question 8

Which of the following best describes how enzymes speed up chemical reactions?

Accepted Answer

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

Question 9

Which of the following scenarios illustrates enzyme specificity and the induced fit model?

Accepted Answer

An enzyme's active site changes shape slightly to fit the substrate more snugly upon binding.

Question 10

A scientist adds a competitive inhibitor to an enzyme-catalyzed reaction. Which of the following will most likely restore the enzyme's activity?

Accepted Answer

Adding more substrate.

Question 11

Which of the following is an example of allosteric regulation?

Accepted Answer

A regulatory molecule binds to a site other than the active site, changing the enzyme's shape and activity.

Question 12

Which of the following best explains why reactions in a closed system eventually reach equilibrium and do no work?

Accepted Answer

At equilibrium, $$\Delta G = 0$$ and there is no net change in free energy to drive work.

Question 13

Which of the following environmental factors can affect enzyme activity by altering the enzyme's three-dimensional structure?

Accepted Answer

Temperature and pH.

Question 14

In feedback inhibition, how does the end product of a metabolic pathway regulate the pathway?

Accepted Answer

It binds to an allosteric site on an enzyme earlier in the pathway, inhibiting its activity.

Question 15

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

Accepted Answer

Exergonic reactions have $$\Delta G  0$$ and require energy input.

Question 16

Which of the following best describes the role of cofactors in enzyme activity?

Accepted Answer

Cofactors are nonprotein helpers that are required for some enzymes to function properly.

Question 17

Hemoglobin exhibits cooperativity. What does this mean in terms of oxygen binding?

Accepted Answer

Binding of one oxygen molecule increases the affinity for additional oxygen molecules.

Question 18

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

Accepted Answer

Changing the overall free energy ($$\Delta G) of $$the reaction.

Question 19

A noncompetitive inhibitor decreases the rate of an enzyme-catalyzed reaction by:

Accepted Answer

Binding to a site other than the active site, changing the enzyme's shape so it cannot catalyze the reaction efficiently.

Question 20

Which of the following best explains why ATP is considered the 'energy currency' of the cell?

Accepted Answer

ATP hydrolysis releases energy that can be coupled to drive endergonic reactions.

Metabolism: Energy Transformation and Enzyme Regulation

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