Question 1

Which of the following best describes the role of a coenzyme in enzymatic reactions?

Accepted Answer

It is a non-protein organic molecule that acts as a transient carrier of specific atoms or functional groups during the reaction.

Question 2

Which enzyme classification is responsible for transferring phosphate groups between molecules?

Accepted Answer

Transferases

Question 3

According to the induced fit model of enzyme-substrate interaction, what happens when the substrate binds to the enzyme?

Accepted Answer

The enzyme undergoes a conformational change to better accommodate the substrate, stabilizing the transition state.

Question 4

Which of the following statements about enzymes and reaction equilibrium is correct?

Accepted Answer

Enzymes accelerate the attainment of equilibrium but do not shift its position.

Question 5

Which equation correctly relates the standard free energy change $\Delta G^{\circ}$ to the equilibrium constant $K_{eq}$ at temperature $T$?

Accepted Answer

$\Delta G^{\circ} = -RT \ln K_{eq}$

Question 6

A scientist is studying an enzyme-catalyzed reaction and observes that increasing substrate concentration beyond a certain point does not increase the reaction rate. What is the most likely explanation?

Accepted Answer

The enzyme has reached saturation; all active sites are occupied.

Question 7

Which of the following is NOT a function of binding energy in enzyme catalysis?

Accepted Answer

Increasing the entropy of the system.

Question 8

Which of the following best describes the transition state in an enzyme-catalyzed reaction?

Accepted Answer

It is a high-energy, unstable state where old bonds are partially broken and new bonds are partially formed.

Question 9

Which of the following is true regarding the Michaelis-Menten constant $K_m$?

Accepted Answer

It is the substrate concentration at which the reaction rate is half of $V_{max}$.

Question 10

Which of the following is the correct Michaelis-Menten equation for initial velocity $v$ as a function of substrate concentration $[S]$?

Accepted Answer

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

Question 11

A researcher plots $1/v$ versus $1/[S]$ for an enzyme-catalyzed reaction. What type of plot is this, and what information can be obtained from it?

Accepted Answer

A Lineweaver-Burk plot; it allows determination of $V_{max}$ and $K_m$ from the intercepts.

Question 12

Which of the following statements about holoenzymes is correct?

Accepted Answer

A holoenzyme is the complete, catalytically active enzyme including all required cofactors.

Question 13

Which of the following is a correct example of an oxidoreductase reaction?

Accepted Answer

Transfer of electrons (hydride ions or H atoms) from one molecule to another.

Question 14

Which of the following is a key difference between the lock-and-key and induced fit models of enzyme action?

Accepted Answer

The induced fit model proposes that the enzyme changes shape to fit the substrate, while the lock-and-key model suggests a rigid fit.

Question 15

Which of the following is true about the specificity of enzyme binding sites?

Accepted Answer

Enzyme binding sites are highly specific, often recognizing only one substrate or a group of closely related substrates.

Question 16

Which of the following is a consequence of the high specificity of enzymes?

Accepted Answer

Enzymes can distinguish between substrates/reactants with similar structures.

Question 17

Which of the following is a correct statement about the effect of enzymes on activation energy?

Accepted Answer

Enzymes lower the activation energy, making reactions proceed faster.

Question 18

Which of the following is a correct description of a lyase enzyme?

Accepted Answer

It catalyzes the cleavage of C–C, C–O, or C–N bonds by elimination, leaving double bonds or rings.

Question 19

A patient is diagnosed with a deficiency in a specific cofactor required for an enzyme involved in energy metabolism. Which of the following is most likely to occur?

Accepted Answer

The enzyme will be inactive or have reduced activity due to lack of the cofactor.

Enzymes: Classification, Mechanisms, and Catalysis

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