Question 1

Which of the following best describes how enzymes affect the activation energy of a chemical reaction, as shown in the first image?

Accepted Answer

Enzymes lower the activation energy, allowing reactions to proceed faster.

Question 2

What is the primary structural feature of an enzyme that determines its specificity for a substrate?

Accepted Answer

The shape of the enzyme's active site.

Question 3

Refer to the second image. What process is illustrated, and what is its effect on enzyme activity?

Accepted Answer

Denaturation; decreases or destroys enzyme activity.

Question 4

Which of the following equations correctly represents the effect of an enzyme on the activation energy ($$E_a) of a $$reaction?

Accepted Answer

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

Question 5

A patient is unable to digest milk due to a deficiency in a specific enzyme. Which enzyme is most likely deficient, and what is its function?

Accepted Answer

Lactase; breaks down lactose into glucose and galactose.

Question 6

Which of the following best explains why cooked egg whites turn from transparent to opaque, based on protein structure?

Accepted Answer

Proteins denature and tangle, scattering light.

Question 7

Which enzyme would be most active at a pH of 2.0, and where is it found in the human body?

Accepted Answer

Pepsin; stomach

Question 8

According to the third image, what happens to the reaction rate as substrate concentration increases beyond the saturation point?

Accepted Answer

The reaction rate plateaus and does not increase further.

Question 9

Which of the following best describes the catalytic cycle of an enzyme?

Accepted Answer

The enzyme binds the substrate, catalyzes the reaction, releases the product, and is reused.

Question 10

A scientist increases the enzyme concentration in a reaction while keeping substrate in excess. What is the expected effect on the reaction rate?

Accepted Answer

The reaction rate will increase proportionally.

Question 11

Which of the following is a correct statement about enzyme denaturation?

Accepted Answer

Denaturation involves the breaking of hydrogen bonds, causing loss of function.

Question 12

Which enzyme is responsible for synthesizing new DNA strands during cell division?

Accepted Answer

DNA Polymerase

Question 13

A reaction in the human body is extremely slow without an enzyme, but occurs in milliseconds with one. What property of enzymes explains this?

Accepted Answer

Enzymes lower the activation energy required for the reaction.

Question 14

Which of the following best describes the effect of pH on enzyme activity?

Accepted Answer

Each enzyme has an optimal pH range where it is most active.

Question 15

Which enzyme protects cells by breaking down hydrogen peroxide into water and oxygen?

Accepted Answer

Catalase

Question 16

A student adds more substrate to a reaction mixture, but the reaction rate does not increase. What is the most likely explanation?

Accepted Answer

All enzyme active sites are saturated.

Question 17

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

Accepted Answer

Enzymes are regenerated after each reaction cycle.

Question 18

Which enzyme is most likely to be inactive at a pH of 10.0?

Accepted Answer

Pepsin

Question 19

Which of the following best describes the relationship between enzyme concentration and reaction rate when substrate is in excess?

Accepted Answer

The reaction rate increases linearly with enzyme concentration.

Question 20

Which of the following steps is NOT part of the enzyme catalytic cycle?

Accepted Answer

Enzyme denaturation

Enzymes and Biological Catalysis: Structure, Function, and Factors Affecting Activity

Study Guide - Practice Questions