Question 1

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

Accepted Answer

Catabolic pathways break down molecules to release energy, which is then used by anabolic pathways to build larger molecules.

Question 2

A metabolic pathway converts a starting molecule into a product through a series of intermediates. Which of the following is TRUE about metabolic pathways?

Accepted Answer

Each reaction in a pathway is catalyzed by a specific enzyme.

Question 3

Which of the following reactions is an example of a hydrolysis reaction?

Accepted Answer

$$\mathrm{XY + H_2O \rightarrow X{-}OH + H{-}Y}$$

Question 4

Which of the following best explains why increasing temperature generally increases the rate of a chemical reaction?

Accepted Answer

It increases the kinetic energy of reactant molecules, allowing more to reach or exceed the activation energy ($$E_a).$$

Question 5

Which of the following statements about enzymes is CORRECT?

Accepted Answer

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

Question 6

A patient is diagnosed with a deficiency in thiamine (vitamin B$$_1). $$Which of the following best explains the likely effect on their metabolism?

Accepted Answer

They will have impaired function of enzymes that require thiamine pyrophosphate (TPP) as a cofactor.

Question 7

Which of the following best describes the effect of increasing substrate concentration on the rate of an enzyme-catalyzed reaction?

Accepted Answer

The reaction rate increases rapidly at first, then levels off as the enzyme becomes saturated.

Question 8

Which of the following is a property of all catalysts, including enzymes?

Accepted Answer

They lower the activation energy ($$E_a) of a $$reaction.

Question 9

Which of the following mechanisms is NOT a way that enzymes facilitate the formation of the transition state?

Accepted Answer

Increasing the activation energy ($$E_a)$$

Question 10

A competitive inhibitor of an enzyme acts by:

Accepted Answer

Binding to the enzyme's active site and preventing substrate binding.

Question 11

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

Accepted Answer

The end product of a pathway inhibits an enzyme that catalyzes an early, committed step.

Question 12

Which of the following is an example of a group transfer reaction?

Accepted Answer

$$\mathrm{X + YZ \rightarrow XZ + Y}$$

Question 13

Which of the following statements about enzyme specificity is TRUE?

Accepted Answer

Some enzymes can catalyze similar reactions for a family of related substrates.

Question 14

Which of the following is a likely consequence of a mutation that alters the amino acids in the active site of an enzyme?

Accepted Answer

The enzyme's catalytic activity may decrease or be lost.

Question 15

Which of the following best explains why enzymes have an optimum temperature and pH?

Accepted Answer

Enzyme structure and activity depend on non-covalent interactions that can be disrupted by changes in temperature and pH.

Question 16

Which of the following is an example of allosteric regulation?

Accepted Answer

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

Question 17

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

Accepted Answer

A catalyst lowers $$E_a$$ but does not change $$\Delta G.$$

Question 18

Which of the following is a function of cofactors in enzyme-catalyzed reactions?

Accepted Answer

They facilitate substrate binding and/or participate directly in catalysis.

Question 19

Which of the following regulatory mechanisms is most likely to be reversible and allow rapid adaptation to changing cellular conditions?

Accepted Answer

Allosteric regulation by small molecules.

Metabolism and Enzyme Function in Cell Biology

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