Question 1

Which of the following best describes an apoenzyme?

Accepted Answer

A protein portion of an enzyme that requires a co-factor to be active.

Question 2

A holoenzyme consists of:

Accepted Answer

An apoenzyme and its required co-factor(s).

Question 3

In the energy diagram shown, what does point 3 represent?

Accepted Answer

The activation energy required for the reaction.

Question 4

Which reaction in the energy diagram is most likely catalyzed by an enzyme, reaction 1 or reaction 2? Why?

Accepted Answer

Reaction 2, because it has a lower activation energy.

Question 5

Is the reaction shown in the energy diagram exergonic or endergonic? Use the following equation: $$\Delta G = G_{products} - G_{reactants}$$

Accepted Answer

Exergonic, because $$\Delta G is $$negative.

Question 6

Which of the following best describes the role of the active site in enzyme catalysis?

Accepted Answer

It is the region where the substrate binds and the reaction occurs.

Question 7

When an enzyme undergoes a conformational change upon substrate binding, this is known as:

Accepted Answer

Induced fit model.

Question 8

Which panel (A, B, or C) in the enzyme diagrams shows the effect of a competitive inhibitor?

Accepted Answer

Panel B

Question 9

In the pH graph, what is happening in area 'A'?

Accepted Answer

Enzyme activity is increasing as pH approaches the optimum.

Question 10

In the temperature graph, what is happening in area 'B'?

Accepted Answer

Enzyme activity is decreasing due to denaturation at high temperatures.

Question 11

Which of the following statements about non-competitive inhibitors is correct?

Accepted Answer

They bind to a site other than the active site and decrease enzyme activity.

Question 12

If the substrate concentration is very high, which type of inhibitor will have the least effect on enzyme activity?

Accepted Answer

Competitive inhibitor

Question 13

Which of the following best explains why enzymes are specific to their substrates?

Accepted Answer

The shape and chemical properties of the active site match only certain substrates.

Question 14

Which of the following is true about the effect of substrate concentration on enzyme activity, as shown in the graph?

Accepted Answer

Enzyme activity increases with substrate concentration until it reaches a maximum rate.

Question 15

A student adds more substrate to a reaction with a fixed amount of enzyme and observes no increase in reaction rate. What is the most likely explanation?

Accepted Answer

The enzyme is saturated; all active sites are occupied.

Question 16

Which of the following equations correctly represents the overall energy released during a reaction?

Accepted Answer

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

Question 17

Which of the following is a real-world example of enzyme denaturation?

Accepted Answer

Cooking an egg causes the proteins to denature and solidify.

Question 18

Which of the following best describes the effect of a competitive inhibitor on enzyme kinetics?

Accepted Answer

It increases the apparent $$K_m$$ but does not affect $$V_{max}.$$

Question 19

Which of the following is NOT a function of a co-factor in enzyme activity?

Accepted Answer

Acting as a competitive inhibitor.

Enzymes: Structure, Function, and Regulation

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