Question 1

In order for an enzymatic reaction obeying the Michaelis-Menten equation to reach 3/4 of its maximum velocity,

Accepted Answer

According to the Michaelis-Menten equation, the reaction velocity (V) is equal to Vmax times [S] divided by the sum of the Michaelis constant (Km) and [S]. At 3/4 of the maximum velocity, V=3/4Vmax. Therefore, we can set up the following equation:

3/4Vmax = Vmax [S] / (Km + [S])

Simplifying this equation gives:

3/4 = [S] / (Km + [S])

Multiplying both sides by (Km + [S]) gives:

3/4 Km + 3/4 [S] = [S]

Subtracting 3/4 [S] from both sides gives:

3/4 Km = 1/4 [S]

Multiplying both sides by 4/3 gives:

[S] = 3/4 Km

Therefore, the answer is choice C.

Question 2

Matching
-Different enzymes that catalyze the same reaction, although may be found in different tissues, are known as ______.

Accepted Answer

Isozymes are different forms of enzymes that catalyze the same reaction but may vary in their amino acid sequence and/or regulatory properties. They may be found in different tissues or organs and can be used to diagnose certain diseases or conditions.

Question 3

Matching -The type of enzyme inhibition in which V_max is unaffected is ______.

Accepted Answer

Competitive inhibition is the type of enzyme inhibition in which V_max is unaffected.

Question 4

Matching
-A lead compound for a new drug should bind to its target protein with a very ______.

Accepted Answer

A small KS (dissociation constant) indicates a strong binding affinity between the lead compound and its target protein.

Question 5

Matching
-In ______, the inhibitor binds to a site involved in both substrate binding and catalysis.

Accepted Answer

Competitive inhibition occurs when the inhibitor binds to the active site of the enzyme, preventing the substrate from binding. This is in contrast to uncompetitive inhibition, where the inhibitor binds to a different site on the enzyme and only after the substrate has bound.

Question 6

Matching
-Assume a first order reaction, the rate of the reaction 2A$\rarr$B is dependent on ______.

Accepted Answer

The rate of a first order reaction is dependent on the concentration of the reactant (in this case, [A]). The rate constant is a property of the reaction and does not change with concentration. Isozymes, Ping Pong, bimolecular, ES complex, random ordered, phosphorylation, small KS, large KS, competitive inhibition, uncompetitive inhibition, and [A]² are not directly related to the dependence of the rate on concentration.

Question 7

Matching
-If A$\rarr$B is a zero-order reaction, the rate is dependent on ______.

Accepted Answer

In a zero-order reaction, the rate is independent of the concentration of reactants and is only dependent on the rate constant.

Question 8

K<sub>M</sub> is

Accepted Answer

K_M is the [S] that half-saturates the enzyme, also known as the Michaelis constant.

Question 9

For a reaction A + B $\rightarrow$ C, if the concentration of B is much larger than A so that [B] remains constant during the reaction while [A] is varied, the kinetics will be

Accepted Answer

Since the concentration of B remains constant, the reaction will exhibit pseudo-first-order kinetics with respect to A. This means that the observed rate of the reaction will be proportional to the concentration of A raised to the first power (i.e., first-order kinetics). The overall rate expression will be rate = k[A][B] (where [B] is constant), which simplifies to rate = k'[A], with k' = k[B]. This is a common situation in enzyme-catalyzed reactions, where one substrate is present at much higher concentrations than the other(s).

Question 10

Matching
-In uncompetitive inhibition, the inhibitor binds only to the ______.

Accepted Answer

In uncompetitive inhibition, the inhibitor binds only to the enzyme-substrate (ES) complex, preventing the complex from converting to product.

Question 11

The K_M can be considered to be the same as the dissociation constant K_S for E + S binding if

Accepted Answer

The answer of The K_M can be considered to be...

Question 12

Find k_cat for a reaction in which V_max is 4 × 10^-4 mol•min^-1 and the reaction mixture contains one microgram of enzyme (the molecular weight of the enzyme is 200,000D).

Accepted Answer

To find k_cat, use the formula k_cat = V_max / [E]. First, convert 1 microgram of enzyme to moles: (1 × 10^-6 g) / (200,000 g/mol) = 5 × 10^-12 mol. Then, k_cat = (4 × 10^-4 mol/min) / (5 × 10^-12 mol) = 8 × 10⁷ min^-1.

Question 13

Find the initial velocity for an enzymatic reaction when V_max = 6.5 × 10^-5 mol•sec^-1, [S] = 3.0 × 10^-3 M, K_M = 4.5 × 10^-3 M and the enzyme concentration at time zero is 1.5 × 10^-2 $\mu$M.

Accepted Answer

The initial velocity can be calculated using the Michaelis-Menten equation:

v0 = (VS1U1B1max [S]) / (KS1U1B1M + [S])

Plugging in the given values:

v0 = (6.5 × 10^-5 mol•sec^-1) (3.0 × 10^-3 M) / (4.5 × 10^-3 M + 3.0 × 10^-3 M)

Simplifying:

v0 = 2.6 × 10^-5 mol•sec^-1

Therefore, the answer is B.

Question 14

Reaction that is first order with respect to A and B

Accepted Answer

A reaction that is first order with respect to both A and B means that the rate of the reaction depends on the concentration of both A and B.

Question 15

A lead compound would be most promising if it had:

Accepted Answer

The answer of A lead compound would be most promising...

Question 16

What is the velocity of a first-order reaction at 37^oC when the reactant concentration is 6 × 10^-2 M and the rate constant is 8 × 10³ sec^-1?

Accepted Answer

The answer of What is the velocity of a first-order...

Question 17

Matching
-A common type of covalent modification of regulatory enzymes involves ______ of serine residues.

Accepted Answer

Covalent modification of regulatory enzymes commonly involves phosphorylation of serine residues.

Question 18

An enzyme is near maximum efficiency when

Accepted Answer

Option B represents the Michaelis-Menten constant (K_M) and the turnover number (k_cat) of an enzyme. When the ratio of these two parameters is approximately 10^8–10^9 M^-1s^-1, an enzyme is near maximum efficiency. This is because this ratio represents the diffusion-controlled limit, which is the fastest possible rate at which an enzyme-substrate interaction can occur. Options A, C, D, and E do not accurately represent the factors that determine an enzyme's maximum efficiency.

Question 19

Matching
-A two-substrate enzymatic reaction in which one product is produced before the second substrate binds to the enzyme has a ______ mechanism.

Accepted Answer

A two-substrate enzymatic reaction in which one product is produced before the second substrate binds to the enzyme has a Ping Pong mechanism. In this type of mechanism, the enzyme first binds with the first substrate, and then releases a product before binding with the second substrate.

Question 20

Matching
-The E+S$\rarr$ E+P reaction is ______.

Accepted Answer

The reaction E+S→E+P is a bimolecular reaction because it involves two reactants, enzyme (E) and substrate (S), coming together to form a product (P).

Quiz 12: Enzyme Kinetics, Inhibition and Control

In order for an enzymatic reaction obeying the Michaelis-Menten equation to reach 3/4 of its maximum velocity,

Matching -Different enzymes that catalyze the same reaction, although may be found in different tissues, are known as ______.

Matching -The type of enzyme inhibition in which V_max is unaffected is ______.

Matching -A lead compound for a new drug should bind to its target protein with a very ______.

Matching -In ______, the inhibitor binds to a site involved in both substrate binding and catalysis.

Matching -Assume a first order reaction, the rate of the reaction 2A $\rarr$ B is dependent on ______.

Matching -If A $\rarr$ B is a zero-order reaction, the rate is dependent on ______.

K_M is

For a reaction A + B $\rightarrow$ C, if the concentration of B is much larger than A so that [B] remains constant during the reaction while [A] is varied, the kinetics will be

Matching -In uncompetitive inhibition, the inhibitor binds only to the ______.

The K_M can be considered to be the same as the dissociation constant K_S for E + S binding if

Find k_cat for a reaction in which V_max is 4 × 10^-4 mol•min^-1 and the reaction mixture contains one microgram of enzyme (the molecular weight of the enzyme is 200,000D) .

Find the initial velocity for an enzymatic reaction when V_max = 6.5 × 10^-5 mol•sec^-1, [S] = 3.0 × 10^-3 M, K_M = 4.5 × 10^-3 M and the enzyme concentration at time zero is 1.5 × 10^-2 $\mu$ M.

Reaction that is first order with respect to A and B

A lead compound would be most promising if it had:

What is the velocity of a first-order reaction at 37^oC when the reactant concentration is 6 × 10^-2 M and the rate constant is 8 × 10³ sec^-1?

Matching -A common type of covalent modification of regulatory enzymes involves ______ of serine residues.

An enzyme is near maximum efficiency when

Matching -A two-substrate enzymatic reaction in which one product is produced before the second substrate binds to the enzyme has a ______ mechanism.

Matching -The E+S $\rarr$ E+P reaction is ______.

Quiz 12: Enzyme Kinetics, Inhibition and Control

In order for an enzymatic reaction obeying the Michaelis-Menten equation to reach 3/4 of its maximum velocity,

Matching -Different enzymes that catalyze the same reaction, although may be found in different tissues, are known as ______.

Matching -The type of enzyme inhibition in which Vmax is unaffected is ______.

Matching -A lead compound for a new drug should bind to its target protein with a very ______.

Matching -In ______, the inhibitor binds to a site involved in both substrate binding and catalysis.

Matching -Assume a first order reaction, the rate of the reaction 2A →\rarr→ B is dependent on ______.

Matching -If A →\rarr→ B is a zero-order reaction, the rate is dependent on ______.

KM is

For a reaction A + B →\rightarrow→ C, if the concentration of B is much larger than A so that [B] remains constant during the reaction while [A] is varied, the kinetics will be

Matching -In uncompetitive inhibition, the inhibitor binds only to the ______.

The KM can be considered to be the same as the dissociation constant KS for E + S binding if

Find kcat for a reaction in which Vmax is 4 × 10-4 mol•min-1 and the reaction mixture contains one microgram of enzyme (the molecular weight of the enzyme is 200,000D) .

Find the initial velocity for an enzymatic reaction when Vmax = 6.5 × 10-5 mol•sec-1, [S] = 3.0 × 10-3 M, KM = 4.5 × 10-3 M and the enzyme concentration at time zero is 1.5 × 10-2 μ\muμ M.

Reaction that is first order with respect to A and B

A lead compound would be most promising if it had:

What is the velocity of a first-order reaction at 37oC when the reactant concentration is 6 × 10-2 M and the rate constant is 8 × 103 sec-1?

Matching -A common type of covalent modification of regulatory enzymes involves ______ of serine residues.

An enzyme is near maximum efficiency when

Matching -A two-substrate enzymatic reaction in which one product is produced before the second substrate binds to the enzyme has a ______ mechanism.

Matching -The E+S →\rarr→ E+P reaction is ______.

Matching -The type of enzyme inhibition in which V_max is unaffected is ______.

Matching -Assume a first order reaction, the rate of the reaction 2A $\rarr$ B is dependent on ______.

Matching -If A $\rarr$ B is a zero-order reaction, the rate is dependent on ______.

K_M is

For a reaction A + B $\rightarrow$ C, if the concentration of B is much larger than A so that [B] remains constant during the reaction while [A] is varied, the kinetics will be

The K_M can be considered to be the same as the dissociation constant K_S for E + S binding if

Find k_cat for a reaction in which V_max is 4 × 10^-4 mol•min^-1 and the reaction mixture contains one microgram of enzyme (the molecular weight of the enzyme is 200,000D) .

Find the initial velocity for an enzymatic reaction when V_max = 6.5 × 10^-5 mol•sec^-1, [S] = 3.0 × 10^-3 M, K_M = 4.5 × 10^-3 M and the enzyme concentration at time zero is 1.5 × 10^-2 $\mu$ M.

What is the velocity of a first-order reaction at 37^oC when the reactant concentration is 6 × 10^-2 M and the rate constant is 8 × 10³ sec^-1?

Matching -The E+S $\rarr$ E+P reaction is ______.