Question 1

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

Accepted Answer

$K_m$ is the substrate concentration at which the enzyme is half-saturated and functions efficiently.

Question 2

Given the Michaelis-Menten equation $v = \frac{V_{max}[S]}{K_m + [S]}$, what happens to the initial velocity ($v$) when $[S] \gg K_m$?

Accepted Answer

$v$ approaches $V_{max}$.

Question 3

An individual has a mutation in the mitochondrial aldehyde dehydrogenase, resulting in a less active enzyme. What is the physiological consequence after alcohol consumption?

Accepted Answer

Acetaldehyde accumulates, causing facial flushing and rapid heart rate.

Question 4

Which equation correctly defines the turnover number ($k_{cat}$) of an enzyme?

Accepted Answer

$k_{cat} = \frac{V_{max}}{[E_t]}$

Question 5

What does the specificity constant ($k_{cat}/K_m$) represent in enzyme kinetics?

Accepted Answer

The catalytic efficiency of the enzyme, especially at low substrate concentrations.

Question 6

Which of the following statements about the diffusion limit in enzyme catalysis is correct?

Accepted Answer

It is the rate at which substrate and enzyme can encounter each other in solution.

Question 7

In a Lineweaver-Burk plot, which of the following is true?

Accepted Answer

The slope equals $K_m/V_{max}$ and the y-intercept equals $1/V_{max}$.

Question 8

Which mechanism describes a reaction where two substrates bind to the enzyme in a random order before catalysis?

Accepted Answer

Random sequential mechanism

Question 9

A double-reciprocal (Lineweaver-Burk) plot of $1/v$ vs $1/[S]$ for an enzyme-catalyzed reaction yields a straight line. What does the x-intercept represent?

Accepted Answer

$-1/K_m$

Question 10

Which of the following best explains why $K_m$ cannot always be considered a simple measure of substrate binding affinity?

Accepted Answer

$K_m$ is a composite constant involving multiple rate constants, not just binding.

Question 11

Which of the following enzymes has the highest turnover number ($k_{cat}$) according to the provided data?

Accepted Answer

Catalase

Question 12

If an enzyme has a very high $k_{cat}$ but also a very high $K_m$, what can be inferred about its catalytic efficiency?

Accepted Answer

It is not easily saturated and may not utilize its full catalytic capacity at low substrate concentrations.

Question 13

Which of the following is a characteristic of a double-displacement (ping-pong) mechanism in enzyme catalysis?

Accepted Answer

One substrate binds and is released before the second substrate binds.

Question 14

Transient (pre-steady state) kinetics are useful for:

Accepted Answer

Revealing the rates of individual steps in an enzyme-catalyzed reaction.

Question 15

Which of the following equations correctly represents the Michaelis-Menten rate equation?

Accepted Answer

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

Question 16

Which of the following statements about the physiological effects of acetaldehyde accumulation is correct?

Accepted Answer

It causes facial flushing and rapid heart rate.

Question 17

If an enzyme operates at the diffusion limit, what does this imply about its catalytic efficiency?

Accepted Answer

Its $k_{cat}/K_m$ is close to $10^8$ to $10^9$ M$^{-1}$s$^{-1}$.

Question 18

Which of the following is true regarding the initial velocity ($v_0$) in Michaelis-Menten kinetics?

Accepted Answer

It is measured before significant product accumulates.

Question 19

In a two-substrate reaction, which experimental observation would suggest the formation of a ternary complex?

Accepted Answer

Intersecting lines in double-reciprocal plots when varying one substrate at different fixed concentrations of the other.

Enzyme Kinetics: Advanced Concepts and Applications

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