Question 1

Which of the following best describes how enzymes speed up chemical reactions in living organisms?

Accepted Answer

They lower the activation energy ($$E_a) $$required to reach the transition state.

Question 2

A scientist is studying an enzyme-catalyzed reaction and observes that increasing substrate concentration increases the reaction rate only up to a certain point, after which the rate levels off. What is the most likely explanation for this observation?

Accepted Answer

The enzyme's active sites are saturated and all are occupied by substrate.

Question 3

Which of the following statements about enzyme specificity is correct?

Accepted Answer

Enzyme specificity is determined by the structure of the enzyme's active site.

Question 4

A patient has a genetic mutation that prevents the production of a required metal ion cofactor for a key metabolic enzyme. What is the most likely consequence?

Accepted Answer

The enzyme will be unable to stabilize the substrate or carry out redox reactions.

Question 5

Which of the following best explains why most biological reactions require enzymes to occur at meaningful rates?

Accepted Answer

Reactants rarely collide with enough kinetic energy and in the correct orientation without enzymes.

Question 6

Which of the following is an example of competitive inhibition?

Accepted Answer

A molecule similar in shape to the substrate binds to the enzyme's active site, blocking substrate binding.

Question 7

An enzyme functions optimally at pH 2. What would most likely happen to its activity if the pH is increased to 7?

Accepted Answer

The enzyme's activity would decrease due to denaturation or altered active site structure.

Question 8

Which of the following best describes the role of coenzymes in enzyme function?

Accepted Answer

Coenzymes are small organic molecules that act as activated carriers, often derived from B vitamins.

Question 9

A researcher adds a molecule to an enzyme-catalyzed reaction that binds to the enzyme at a site other than the active site, causing a conformational change. What type of regulation is this?

Accepted Answer

Allosteric regulation

Question 10

Which of the following statements about the effect of temperature on enzyme activity is correct?

Accepted Answer

Enzyme activity is highest at the enzyme's optimal temperature and decreases if the temperature is too high or too low.

Question 11

During a reaction catalyzed by an enzyme, which of the following is true about the enzyme's role in the reaction's free energy change ($$\Delta G$$)?

Accepted Answer

The enzyme does not change $$\Delta G$$; it only lowers the activation energy ($$E_a).$$

Question 12

A new drug is found to bind irreversibly to the active site of an essential bacterial enzyme. Which of the following best describes the effect of this drug?

Accepted Answer

It permanently inactivates the enzyme by blocking the active site.

Question 13

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

Accepted Answer

Enzymes are regenerated after each reaction cycle and can catalyze multiple rounds of substrate conversion.

Question 14

A mutation alters the amino acid sequence of an enzyme's active site. Which of the following is the most likely result?

Accepted Answer

The enzyme's specificity and catalytic activity may be reduced or lost.

Question 15

Which of the following is true regarding the transition state in an enzyme-catalyzed reaction?

Accepted Answer

The transition state is a hypothetical high-energy state that enzymes help substrates achieve.

Question 16

A patient is given a drug that acts as a competitive inhibitor for an enzyme involved in blood clotting. Which of the following would most likely increase the effectiveness of the enzyme in the presence of this drug?

Accepted Answer

Increasing the concentration of the substrate.

Question 17

Which of the following best describes the effect of a high-affinity enzyme compared to a low-affinity enzyme?

Accepted Answer

A high-affinity enzyme reaches its maximum rate ($$V_{max}) at a $$lower substrate concentration.

Question 18

Which of the following scenarios best illustrates allosteric regulation of an enzyme?

Accepted Answer

A molecule binds to a site other than the active site, causing a conformational change that affects enzyme activity.

Question 19

A metabolic pathway in a cell is regulated by feedback inhibition. Which of the following best describes this process?

Accepted Answer

The final product of the pathway binds allosterically to an enzyme early in the pathway, reducing its activity.

BIO181- 3.2: Enzymes (UNIT3-Energy & Metabolism)

Guida di studio - Domande di pratica

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