Question 1

Based on the Michaelis-Menten plot for WT Sparty enzyme, which of the following best describes the effect of a competitive inhibitor on the $$V_{max}$$ and $$K_m$$ values?

Accepted Answer

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

Question 2

If an uncompetitive inhibitor is added to the WT Sparty enzyme reaction, what would you expect to see in the Lineweaver-Burk plot?

Accepted Answer

Parallel lines with both $$V_{max}$$ and $$K_m$$ decreased

Question 3

Given the WT Sparty enzyme has $$k_{cat} = 10^5$ 	ext{ s}^{-1}$$ and $$K_m = 5 	ext{ }	ext{	extmu M}$$, calculate the catalytic efficiency ($$k_{cat}/K_m) in$$ $$	ext{M}^{-1}	ext{s}^{-1}.$$

Accepted Answer

$$2 	imes 10^7$ 	ext{ M}^{-1}	ext{s}^{-1}$$

Question 4

A variant of the GFE enzyme has a $$K_m$$ value of $$50 	ext{ }	ext{	extmu M}$$ and the same $$V_{max} as WT $$Sparty. How does the efficiency of this variant compare to WT Sparty?

Accepted Answer

Less efficient due to higher $$K_m$$

Question 5

In the context of enzyme kinetics, what does the $$K_m$$ value represent?

Accepted Answer

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

Question 6

If a competitive inhibitor is present, how would the Michaelis-Menten curve for WT Sparty change?

Accepted Answer

The curve would reach the same $$V_{max}$$ but require a higher substrate concentration

Question 7

Which of the following statements is true regarding the effect of an uncompetitive inhibitor on enzyme kinetics?

Accepted Answer

Both $$V_{max}$$ and $$K_m$$ decrease

Question 8

A researcher observes that the Lineweaver-Burk plot for an enzyme in the presence of an inhibitor shows lines intersecting at the y-axis. What type of inhibition is most likely occurring?

Accepted Answer

Competitive inhibition

Question 9

If the $$V_{max}$$ for WT Sparty is $$10 	ext{ }	ext{	extmu M/min}$$, what is the initial velocity ($$v_0) at$$ $$[S] = 5 	ext{ }	ext{	extmu M}$$, given $$K_m = 5 	ext{ }	ext{	extmu M}$$? Use the Michaelis-Menten equation: $$v_0$$ = \frac{V_{max}[S]}{K_m + [S]}$$.

Accepted Answer

$$5 	ext{ }	ext{	extmu M/min}$$

Question 10

Which of the following best describes the effect of a noncompetitive inhibitor on the Lineweaver-Burk plot?

Accepted Answer

Lines intersect at the x-axis; $$V_{max}$$ decreases, $$K_m$$ unchanged

Question 11

A patient is treated with a drug that acts as a competitive inhibitor for a key metabolic enzyme. What is the most likely effect on the enzyme's activity at high substrate concentrations?

Accepted Answer

The enzyme will reach the same $$V_{max} as $$without the inhibitor

Question 12

If the WT Sparty enzyme is exposed to an uncompetitive inhibitor, which of the following changes would you expect in the Michaelis-Menten plot?

Accepted Answer

The curve would reach a lower $$V_{max}$$ and require a lower substrate concentration to reach half $$V_{max}$$

Question 13

Which equation correctly represents the Lineweaver-Burk transformation of the Michaelis-Menten equation?

Accepted Answer

$$\frac{1}{v_0$} = \frac{K_m}{V_{max}} \frac{1}{[S]} + \frac{1}{V_{max}}$$

Question 14

A new drug is found to decrease both $$V_{max}$$ and $$K_m$$ for an enzyme. What type of inhibition does this drug most likely exhibit?

Accepted Answer

Uncompetitive inhibition

Question 15

If the $$K_m of an $$enzyme increases in the presence of an inhibitor, but $$V_{max}$$ remains the same, what type of inhibition is occurring?

Accepted Answer

Competitive inhibition

Question 16

A mutation in the Sparty enzyme decreases $$k_{cat} by 50$$% but leaves $$K_m$$ unchanged. What is the effect on catalytic efficiency?

Accepted Answer

Catalytic efficiency is halved

Question 17

Which of the following is the correct definition of $$k_{cat}$$?

Accepted Answer

The number of substrate molecules converted to product per enzyme molecule per second

Question 18

A competitive inhibitor is added to the Sparty enzyme reaction. What would you expect to see in the Lineweaver-Burk plot?

Accepted Answer

Lines intersect at the y-axis, with increased slope

Question 19

If the $$K_m$$ for Sparty enzyme is $$5 	ext{ }	ext{	extmu M}$$ and the substrate concentration is $$50 	ext{ }	ext{	extmu M}$$, what fraction of $$V_{max} is $$achieved? Use the Michaelis-Menten equation.

Accepted Answer

$$\frac{50}{5+50} = \frac{50}{55} \approx 0.91$$

Enzyme Kinetics: Michaelis-Menten and Lineweaver-Burk Analysis

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