Question 1

Which of the following best describes the primary function of enzymes in biological systems?

Accepted Answer

Enzymes speed up chemical reactions by lowering the activation energy.

Question 2

The lock and key hypothesis and the induced fit model both describe enzyme-substrate interactions. Which statement best distinguishes the induced fit model?

Accepted Answer

The enzyme's active site changes shape to better fit the substrate upon binding.

Question 3

Which of the following is most likely to cause denaturation of an enzyme?

Accepted Answer

Extreme changes in pH.

Question 4

A competitive inhibitor affects enzyme activity by:

Accepted Answer

Binding to the active site and preventing substrate binding.

Question 5

Which equation correctly represents the effect of an enzyme on activation energy ($$E_a) in a $$chemical reaction?

Accepted Answer

$$E_{a,enzyme} \u003c E_{a,uncatalyzed}$$

Question 6

Which of the following is a coenzyme that assists enzymes in catalyzing reactions?

Accepted Answer

Vitamin B6 (pyridoxal phosphate)

Question 7

Feedback inhibition in metabolic pathways is best described as:

Accepted Answer

The end product of a pathway inhibits the first enzyme by binding to an allosteric site.

Question 8

Which of the following enzyme types catalyzes the transfer of phosphate groups?

Accepted Answer

Kinase

Question 9

If an enzyme is exposed to a temperature above its optimum, what is the most likely outcome?

Accepted Answer

The enzyme will denature and lose its biological activity.

Question 10

Which statement about enzyme specificity is correct?

Accepted Answer

Enzymes are specific to their substrates due to the shape of their active site.

Question 11

A noncompetitive inhibitor affects enzyme activity by:

Accepted Answer

Binding to an allosteric site and changing the enzyme's shape.

Question 12

Which of the following best explains why enzymes are not consumed in the reactions they catalyze?

Accepted Answer

Enzymes are regenerated after each reaction.

Question 13

Which of the following is most likely to increase the rate of an enzyme-catalyzed reaction, assuming substrate is not limiting?

Accepted Answer

Increasing the concentration of the enzyme.

Question 14

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

Accepted Answer

The enzyme may lose its substrate specificity.

Question 15

Which of the following best describes the role of phosphofructokinase (PFK) in glycolysis?

Accepted Answer

PFK catalyzes the transfer of a phosphate group to fructose-6-phosphate.

Question 16

Which of the following is true regarding the effect of substrate concentration on enzyme activity?

Accepted Answer

Enzyme activity increases with substrate concentration until the enzyme becomes saturated.

Question 17

Which of the following is a real-world example of feedback inhibition?

Accepted Answer

Isoleucine inhibits the first enzyme in its biosynthetic pathway by binding to an allosteric site.

Question 18

Which of the following best explains why enzymes are called biological catalysts?

Accepted Answer

They are made of proteins and speed up chemical reactions without being consumed.

Question 19

Which of the following is most likely to restore the activity of a denatured enzyme under laboratory conditions?

Accepted Answer

Returning the enzyme to its optimum pH and temperature.

Question 20

Which of the following best describes the effect of a cofactor on enzyme activity?

Accepted Answer

A cofactor binds to the enzyme and is required for its catalytic activity.

Enzymes: Structure, Function, and Regulation

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