Question 1

Which of the following statements best describes the role of enzymes in biological reactions?

Accepted Answer

Enzymes lower the activation energy, thereby increasing the rate of both the forward and reverse reactions.

Question 2

A reaction has a negative $$\Delta G$$ but proceeds very slowly in the absence of an enzyme. What is the most likely explanation?

Accepted Answer

The activation energy ($$\Delta G$$^{\ddagger}$$) is high, so the reaction rate is slow.

Question 3

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

Accepted Answer

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

Question 4

In the context of enzyme kinetics, what does a high turnover number ($$k_{cat}) $$indicate?

Accepted Answer

The enzyme converts substrate to product rapidly once bound.

Question 5

Which of the following best explains why the steady-state assumption is used in Michaelis-Menten kinetics?

Accepted Answer

It assumes that the concentration of the enzyme-substrate complex ($$[ES]) $$remains constant during the initial phase of the reaction.

Question 6

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

Accepted Answer

The enzyme is saturated; all active sites are occupied, and the reaction is proceeding at $$V_{max}.$$

Question 7

Which of the following equations correctly relates the rate of an enzyme-catalyzed reaction to substrate concentration according to the Michaelis-Menten model?

Accepted Answer

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

Question 8

Which of the following is a consequence of an enzyme binding the transition state more tightly than the substrate?

Accepted Answer

The activation energy ($$\Delta G$$^{\ddagger}$$) of the reaction is decreased, increasing the reaction rate.

Question 9

Which of the following statements about the 'induced fit' model of enzyme-substrate binding is correct?

Accepted Answer

The enzyme changes conformation upon substrate binding to better accommodate the substrate.

Question 10

A reaction has $$\Delta G = -20 kJ/$$mol. What does this indicate about the reaction?

Accepted Answer

The reaction is exergonic and will proceed spontaneously under standard conditions.

Question 11

Which of the following is true regarding the effect of an enzyme on the thermodynamic parameters of a reaction?

Accepted Answer

An enzyme lowers the activation energy ($$\Delta G$$^{\ddagger}$$) but does not change $$\Delta G$$.

Question 12

In a double-displacement (ping-pong) reaction mechanism, which of the following is true?

Accepted Answer

A covalent enzyme intermediate is formed after the first substrate reacts.

Question 13

Which of the following best describes the specificity of chymotrypsin?

Accepted Answer

Chymotrypsin cleaves peptide bonds adjacent to aromatic amino acids.

Question 14

Which of the following is a correct statement about the effect of increasing enzyme concentration on $$V_{max}$$?

Accepted Answer

$$V_{max}$$ increases as enzyme concentration increases.

Question 15

Which parameter is most useful for comparing the catalytic efficiency of different enzymes?

Accepted Answer

$$k_{cat}/K_m$$

Question 16

In the Michaelis-Menten equation, what does a low $$K_m$$ value indicate about an enzyme?

Accepted Answer

The enzyme has a high affinity for its substrate.

Question 17

Which of the following is true about the effect of a non-aqueous environment on enzyme active sites?

Accepted Answer

Non-aqueous environments favor van der Waals and hydrophobic interactions.

Question 18

Which of the following is a correct statement about the 'lock and key' model of enzyme-substrate binding?

Accepted Answer

The substrate fits into a rigid, pre-formed active site on the enzyme.

Question 19

Which of the following is true regarding the effect of substrate concentration on $$K_m$$?

Accepted Answer

$$K_m is $$independent of substrate concentration.

Enzyme Structure, Function, and Kinetics: Comprehensive Study Notes

Guida di studio - Domande di pratica

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