Question 1

Which of the following statements best describes the role of enzymes in cellular metabolism?

Accepted Answer

Enzymes lower the activation energy barrier, allowing reactions to occur more rapidly and efficiently.

Question 2

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

Accepted Answer

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

Question 3

A cell couples the hydrolysis of ATP to drive an endergonic reaction. Which of the following best explains why this is possible?

Accepted Answer

The hydrolysis of ATP releases energy, which can be used to power reactions with a positive $$\Delta G.$$

Question 4

Which of the following processes is exergonic and releases energy that can be used by the cell?

Accepted Answer

Cellular respiration

Question 5

Consider the reaction: $$	ext{ATP} ightarrow 	ext{ADP} + P_i. $$What is the sign of $$\Delta G$$ for this reaction, and is it exergonic or endergonic?

Accepted Answer

$$\Delta G is $$negative; the reaction is exergonic.

Question 6

Which of the following best describes the effect of an enzyme on the activation energy ($$E_a) $$and the free energy change ($$\Delta G) of a $$reaction?

Accepted Answer

An enzyme lowers $$E_a$$ but does not change $$\Delta G.$$

Question 7

Pepsin is a human enzyme that functions optimally at pH 2. Where in the body is pepsin most likely to be found?

Accepted Answer

In the stomach

Question 8

Which of the following is an example of allosteric regulation in enzymes?

Accepted Answer

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

Question 9

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

Accepted Answer

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

Question 10

A metabolic pathway is regulated by feedback inhibition. Which molecule typically acts as the inhibitor in this process?

Accepted Answer

The final product of the pathway

Question 11

Which of the following best describes the induced fit model of enzyme action?

Accepted Answer

The enzyme changes shape slightly to better fit the substrate upon binding.

Question 12

Which of the following factors would most likely increase the rate of an enzyme-catalyzed reaction, assuming all other conditions are optimal?

Accepted Answer

Increasing the substrate concentration up to saturation

Question 13

Which of the following is true about the second law of thermodynamics as it applies to biological systems?

Accepted Answer

Every energy transfer increases the entropy (disorder) of the universe.

Question 14

Which of the following is an example of energy coupling in cells?

Accepted Answer

Using the energy released from ATP hydrolysis to power active transport of ions

Question 15

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

Accepted Answer

Catabolic pathways break down molecules and release energy, while anabolic pathways build molecules and require energy.

Question 16

Which of the following is NOT a mechanism by which enzymes lower activation energy?

Accepted Answer

Increasing the temperature of the reaction

Question 17

If the free energy change ($$\Delta G) $$for a reaction is negative, which of the following is true?

Accepted Answer

The reaction is spontaneous and releases energy.

Question 18

Which of the following best explains why photosynthesis is considered an 'uphill' reaction?

Accepted Answer

It requires an input of energy to build complex molecules from simple ones.

Question 19

Which of the following statements about cofactors and coenzymes is correct?

Accepted Answer

Cofactors can be either inorganic ions or organic molecules; coenzymes are specifically organic cofactors.

Metabolism, Energy, and Enzyme Function in Cells: Study Guide

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