Question 1

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

Accepted Answer

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

Question 2

A researcher measures the initial velocity ($$v_0) of an $$enzyme-catalyzed reaction at various substrate concentrations. Which equation should they use to model their data according to Michaelis-Menten kinetics?

Accepted Answer

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

Question 3

If an enzyme has a low $$K_m$$ value for a particular substrate, what does this indicate about the enzyme's affinity for that substrate?

Accepted Answer

The enzyme has a high affinity for the substrate.

Question 4

Which of the following statements about $$V_{max} is $$correct?

Accepted Answer

$$V_{max} is $$the maximum velocity achieved by the system, at saturating substrate concentration.

Question 5

A competitive inhibitor affects enzyme kinetics by:

Accepted Answer

Increasing the apparent $$K_m$$ without affecting $$V_{max}.$$

Question 6

Which plot is commonly used to linearize the Michaelis-Menten equation for easier determination of $$K_m$$ and $$V_{max}$$?

Accepted Answer

Lineweaver-Burk plot (double-reciprocal plot)

Question 7

Given the Michaelis-Menten equation $$v_0$$ = \frac{V_{max}[S]}{K_m + [S]}$$, what is the value of v_0$ when $$[S] = K_m$$?

Accepted Answer

$$v_0$$ = \frac{V_{max}}{2}$$

Question 8

Which of the following is true regarding the dissociation constant $$K_D in $$biochemistry?

Accepted Answer

$$K_D is a $$measure of the affinity between two molecules; lower $$K_D$$ means higher affinity.

Question 9

An enzyme is regulated by phosphorylation. Which type of modification is this?

Accepted Answer

Covalent modification

Question 10

Which of the following best describes feedback inhibition in metabolic pathways?

Accepted Answer

The final product of a pathway inhibits an earlier enzyme in the pathway.

Question 11

A noncompetitive inhibitor affects enzyme kinetics by:

Accepted Answer

Decreasing $$V_{max}$$ without changing $$K_m.$$

Question 12

Which of the following is a characteristic of allosteric enzymes?

Accepted Answer

They often have multiple subunits and exhibit cooperativity.

Question 13

Which equation represents the association constant ($$K_{eq}) $$for the reaction $$A + B \leftrightarrow AB$$?

Accepted Answer

$$K_{eq} = \frac{[AB]}{[A][B]}$$

Question 14

Which of the following statements about enzyme saturation is correct?

Accepted Answer

At saturation, all enzyme active sites are occupied by substrate.

Question 15

A patient is given a drug that acts as a reversible inhibitor of an enzyme. Which of the following is most likely true?

Accepted Answer

The inhibitor binds noncovalently and can dissociate from the enzyme.

Question 16

Which of the following is the correct formula for the dissociation constant ($$K_D) $$for the reaction $$AB \leftrightarrow A + B$$?

Accepted Answer

$$K_D = \frac{[A][B]}{[AB]}$$

Question 17

Which of the following is true about the turnover number ($$k_{cat}) of an $$enzyme?

Accepted Answer

$$k_{cat} is $$the number of substrate molecules converted to product per enzyme molecule per unit time.

Question 18

Which of the following best explains why the Lineweaver-Burk plot is useful in enzyme kinetics?

Accepted Answer

It linearizes the Michaelis-Menten equation, making it easier to determine $$K_m$$ and $$V_{max}.$$

Question 19

Which of the following modifications is irreversible and activates enzymes such as trypsin?

Accepted Answer

Proteolytic cleavage

Question 20

In a Lineweaver-Burk plot, what does the y-intercept represent?

Accepted Answer

$$\frac{1}{V_{max}}$$

Enzyme Kinetics and Regulation: Core Concepts in Cell Biology

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