Question 1

Which of the following best describes the primary function of an enzyme in a biological system?

Accepted Answer

Enzymes lower the activation energy, increasing the rate of biochemical reactions.

Question 2

Which of the following is an example of a cofactor that is an inorganic ion?

Accepted Answer

$$Zn^{2+}$$

Question 3

Which enzyme class catalyzes the transfer of functional groups from one molecule to another?

Accepted Answer

Transferases

Question 4

Which of the following statements about enzyme naming is correct?

Accepted Answer

Some enzymes are named based on their function, but exceptions like 'pepsin' exist.

Question 5

According to the lock-and-key model of enzyme action, which statement is true?

Accepted Answer

The enzyme's active site is already in the correct shape for the substrate.

Question 6

Which of the following best describes the induced-fit model of enzyme-substrate interaction?

Accepted Answer

The enzyme's active site changes shape to accommodate the substrate.

Question 7

What is the effect of a positive allosteric regulator on an enzyme?

Accepted Answer

It increases the enzyme's ability to bind the substrate, raising the reaction rate.

Question 8

Which of the following is true about competitive inhibition?

Accepted Answer

The inhibitor competes with the substrate for the active site.

Question 9

A non-competitive inhibitor affects enzyme activity by:

Accepted Answer

Binding to an allosteric site, changing the enzyme's shape so the substrate cannot bind.

Question 10

Which of the following best describes a zymogen?

Accepted Answer

An inactive enzyme precursor that requires cleavage to become active.

Question 11

Pepsin is an example of a(n):

Accepted Answer

Enzyme activated from a zymogen in the stomach by hydrochloric acid.

Question 12

Which of the following graphs best represents the effect of increasing temperature on the rate of a typical human enzyme-catalyzed reaction?

Accepted Answer

A bell-shaped curve with an optimal temperature around 37°C.

Question 13

Which statement best explains why enzymes are highly specific for their substrates?

Accepted Answer

The active site of an enzyme has a unique shape that only fits specific substrates.

Question 14

Which of the following is a real-life example of irreversible enzyme inhibition?

Accepted Answer

Penicillin inhibiting bacterial transpeptidase.

Question 15

A patient is diagnosed with lead poisoning. Lead ions inhibit several enzymes by binding to sulfhydryl groups, causing permanent loss of enzyme activity. What type of inhibition is this?

Accepted Answer

Irreversible inhibition

Question 16

Which equation best 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 17

Which of the following is NOT a class of enzyme according to the international classification system?

Accepted Answer

Polymerases

Question 18

A mutation causes an enzyme's active site to be less complementary to its substrate. Which model of enzyme-substrate interaction is most affected?

Accepted Answer

Lock-and-key model

Question 19

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

Accepted Answer

Each enzyme has an optimal pH at which its activity is maximal.

Question 20

Which of the following scenarios best illustrates negative allosteric control?

Accepted Answer

A molecule binds to an enzyme and decreases its ability to bind the substrate.

Enzymes: Structure, Function, and Regulation

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