Question 1

Which of the following best explains how enzymes speed up chemical reactions in biological systems?

Accepted Answer

They lower the activation energy ($$E_A) $$required for the reaction to proceed.

Question 2

A scientist adds sucrase to a sucrose solution at room temperature. Which of the following best describes what happens?

Accepted Answer

The sucrose is rapidly hydrolyzed into glucose and fructose within seconds.

Question 3

Which statement about activation energy ($$E_A) is $$correct?

Accepted Answer

It is the initial investment of energy required to start a chemical reaction.

Question 4

In a metabolic pathway, the end product binds to the first enzyme at a site other than the active site, causing the enzyme to change shape and reduce its activity. This is an example of:

Accepted Answer

Feedback inhibition

Question 5

Which of the following would most likely increase the rate of an enzyme-catalyzed reaction that is currently saturated with substrate?

Accepted Answer

Adding more enzyme

Question 6

A patient is diagnosed with a genetic mutation that alters the shape of an enzyme's active site. Which of the following is the most likely consequence?

Accepted Answer

The enzyme will have reduced specificity for its substrate.

Question 7

Which of the following best describes the effect of a competitive inhibitor on an enzyme-catalyzed reaction?

Accepted Answer

It binds to the active site, blocking substrate binding, and its effect can be overcome by increasing substrate concentration.

Question 8

Why do enzymes from thermophilic bacteria have higher optimal temperatures than human enzymes?

Accepted Answer

They are adapted to function in hot environments, so their structure is stable and active at higher temperatures.

Question 9

Which of the following statements about enzyme specificity is correct?

Accepted Answer

It results from the complementary fit between the shape of the enzyme's active site and the substrate.

Question 10

A researcher observes that increasing the substrate concentration increases the reaction rate, but only up to a certain point, after which the rate levels off. What is the most likely explanation?

Accepted Answer

The enzyme is saturated; all active sites are occupied.

Question 11

Which of the following best describes the role of cofactors in enzyme activity?

Accepted Answer

They are nonprotein helpers that assist enzymes, and can be inorganic ions or organic coenzymes.

Question 12

A noncompetitive inhibitor decreases the rate of an enzyme-catalyzed reaction by:

Accepted Answer

Binding to a site other than the active site, causing the enzyme to change shape and reducing its activity.

Question 13

Which of the following is true regarding the effect of temperature on enzyme activity?

Accepted Answer

Enzyme activity increases with temperature up to an optimal point, after which activity decreases due to denaturation.

Question 14

Which of the following scenarios best illustrates feedback inhibition in a metabolic pathway?

Accepted Answer

The end product of a pathway binds to the first enzyme, inhibiting its activity.

Question 15

Which of the following changes would NOT be expected to affect the rate of an enzyme-catalyzed reaction in a living cell?

Accepted Answer

Increasing the free energy change ($$\Delta G) of $$the reaction.

Question 16

A mutation in a gene encoding an enzyme changes a single amino acid in the active site. Which property of the enzyme is most likely to be affected?

Accepted Answer

Its affinity for its substrate

Question 17

Which of the following best describes the transition state in a chemical reaction?

Accepted Answer

It is an unstable, high-energy state where bonds can be broken and the reaction can proceed.

Question 18

Which of the following statements about allosteric regulation is correct?

Accepted Answer

A regulatory molecule binds to a site other than the active site, affecting enzyme activity.

Question 19

A metabolic pathway is producing too much of its end product. Which regulatory mechanism is most likely to prevent wasteful overproduction?

Accepted Answer

Feedback inhibition by the end product on the first enzyme of the pathway

Question 20

Which of the following best explains why enzymes are not consumed during the reactions they catalyze?

Accepted Answer

They facilitate the reaction by lowering activation energy but are released unchanged after the reaction.

Introduction to Metabolism Pt. 2

Guida di studio - Domande di pratica

Study guide - Flashcard