Question 1

Which statement best describes how enzymes increase the rate of chemical reactions?

Accepted Answer

They lower the activation energy by stabilizing the transition state.

Question 2

What is the role of a cofactor in enzyme activity?

Accepted Answer

It is a small molecule required for some enzymes to be active.

Question 3

Which of the following best defines the Michaelis constant ($$K_m) in $$enzyme kinetics?

Accepted Answer

The substrate concentration at which the reaction rate is half-maximal.

Question 4

A patient experiences facial flushing and rapid heartbeat after consuming alcohol due to excessive blood acetaldehyde. Which enzyme kinetic property explains this phenomenon?

Accepted Answer

The patient has a form of acetaldehyde dehydrogenase with a high $$K_m$$, resulting in inefficient acetaldehyde processing.

Question 5

Which equation represents the Michaelis-Menten relationship between initial velocity ($$v_0) $$and substrate concentration ($$[S]$$)?

Accepted Answer

$$v_0$$ = \frac{V_{max}[S]}{K_m + [S]}$$

Question 6

Which type of enzyme inhibition can be overcome by increasing substrate concentration?

Accepted Answer

Competitive inhibition

Question 7

What is the effect of a competitive inhibitor on $$K_m$$ and $$V_{max}$$?

Accepted Answer

$$K_m$$ increases, $$V_{max}$$ remains unchanged

Question 8

Which of the following is true about the free energy change ($$\Delta G) of a $$reaction?

Accepted Answer

It determines whether the reaction is spontaneous.

Question 9

Which of the following best describes a holoenzyme?

Accepted Answer

An enzyme with its cofactor, active

Question 10

Which plot is commonly used to determine $$K_m$$ and $$V_{max}$$ from experimental data?

Accepted Answer

Lineweaver-Burk plot

Question 11

A researcher is studying an enzyme that requires Zn$$^{2+}$$ for activity. What would be the effect of removing Zn$$^{2+}$$ from the reaction mixture?

Accepted Answer

The enzyme would become an apoenzyme and lose activity.

Question 12

Which of the following is a real-world example of a suicide inhibitor?

Accepted Answer

Penicillin inhibiting bacterial transpeptidase

Question 13

Which statement about allosteric enzymes is correct?

Accepted Answer

They display cooperative substrate binding and sigmoidal velocity curves.

Question 14

What is the turnover number ($$k_{cat}) of an $$enzyme?

Accepted Answer

The number of substrate molecules converted to product per enzyme molecule per unit time when the enzyme is saturated with substrate.

Question 15

Which of the following is true regarding noncompetitive inhibition?

Accepted Answer

$$V_{max}$$ decreases, $$K_m$$ remains unchanged

Question 16

An enzyme-catalyzed reaction proceeds through a transition state. What is the activation energy ($$\Delta G$$^{\ddagger}$$) for this reaction?

Accepted Answer

$$\Delta G$$^{\ddagger}$$ = G_{X$$^{\ddagger}$$} - G_S$$

Question 17

Which of the following is a characteristic of the active site of an enzyme?

Accepted Answer

It creates a unique microenvironment and involves residues from different parts of the protein.

Question 18

Which type of inhibition is described by an inhibitor binding only to the enzyme-substrate complex, resulting in decreased $$V_{max}$$ and $$K_m$$?

Accepted Answer

Uncompetitive inhibition

Question 19

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

Accepted Answer

The enzyme changes shape to better accommodate the substrate, enhancing catalysis.

Question 20

Which of the following is true about the specificity constant ($$k_{cat}/K_m) $$for an enzyme?

Accepted Answer

It is an apparent second-order rate constant and reflects enzyme efficiency at low substrate concentrations.

Enzymes: Basic Concepts and Kinetics – Study Notes

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