Question 1

Which of the following best describes the difference between anabolic and catabolic reactions in metabolism?

Accepted Answer

Anabolic reactions build larger molecules from smaller ones, requiring energy input, while catabolic reactions break down large molecules into smaller ones, releasing energy.

Question 2

Which statement about enzyme specificity is correct?

Accepted Answer

Enzyme specificity is determined by the three-dimensional conformation of the active site, which is complementary to the substrate in shape, size, charge, and orientation.

Question 3

Which of the following best explains how enzymes lower the activation energy ($$E_A) of a $$reaction?

Accepted Answer

By providing a microenvironment that is conducive for the reaction, orienting substrates correctly, and destabilizing bonds to facilitate the transition state.

Question 4

A scientist is measuring the rate of an enzyme-catalyzed reaction by monitoring the disappearance of substrate over time. Which experimental method is most appropriate for this measurement?

Accepted Answer

Measuring the absorbance of the reaction mixture at fixed intervals using a colorimeter.

Question 5

Which of the following statements about the Michaelis constant ($$K_m) is $$correct?

Accepted Answer

$$K_m$$ indicates the affinity of the enzyme for its substrate; a low $$K_m$$ means high affinity.

Question 6

Which of the following best describes the effect of a competitive inhibitor on enzyme activity?

Accepted Answer

It binds to the active site, increasing $$K_m$$ but not affecting $$V_{max}.$$

Question 7

A patient is exposed to cyanide, which acts as a non-competitive inhibitor of cytochrome oxidase. What is the expected effect on the enzyme kinetics?

Accepted Answer

$$K_m$$ remains unchanged and $$V_{max}$$ decreases.

Question 8

Which of the following is an example of an irreversible inhibitor?

Accepted Answer

Heavy metals such as mercury binding to enzymes and disrupting disulfide bonds.

Question 9

Which of the following best explains why enzyme activity decreases drastically at temperatures above the optimum?

Accepted Answer

The enzyme is denatured due to disruption of hydrogen bonds, ionic bonds, and hydrophobic interactions, altering the active site.

Question 10

Which of the following statements about allosteric regulation is correct?

Accepted Answer

Allosteric regulators bind to a site other than the active site and can either inhibit or activate enzyme activity.

Question 11

A researcher increases the substrate concentration in an enzyme-catalyzed reaction and observes that the reaction rate eventually plateaus. What is the most likely explanation?

Accepted Answer

All active sites of the enzyme are saturated with substrate, so increasing substrate concentration further does not increase the rate.

Question 12

Which of the following best describes the role of a coenzyme in enzyme activity?

Accepted Answer

A coenzyme is an organic molecule that binds loosely to the enzyme and is required for its activity.

Question 13

Which of the following experimental setups would best allow you to measure the initial rate of an enzyme-catalyzed reaction?

Accepted Answer

Measuring the gradient of the linear slope at time = 0 on a graph of product formed versus time.

Question 14

Which of the following is a correct statement about feedback inhibition in metabolic pathways?

Accepted Answer

The end product of a pathway acts as an allosteric inhibitor of an enzyme early in the pathway, decreasing the pathway's activity.

Question 15

Which of the following best describes the effect of pH on enzyme activity?

Accepted Answer

Each enzyme has an optimum pH, and deviations from this pH can reduce activity by altering the charge and conformation of the active site.

Question 16

Which of the following is true regarding the induced fit hypothesis of enzyme action?

Accepted Answer

The enzyme changes shape upon substrate binding, resulting in a precise fit that facilitates catalysis.

Question 17

A mutation causes an enzyme's active site to lose its specific shape. What is the most likely consequence?

Accepted Answer

The enzyme will lose its specificity and may not bind its substrate, reducing or abolishing its catalytic activity.

Question 18

Which of the following best explains why enzymes are effective in small amounts?

Accepted Answer

Enzymes remain chemically unchanged after the reaction and can catalyze many cycles of substrate conversion.

Question 19

Which of the following is an example of cooperativity in enzyme regulation?

Accepted Answer

A substrate binding to one active site of a multi-subunit enzyme increases the affinity of other active sites for additional substrate molecules.

Comprehensive Study Notes on Enzymes

Guida di studio - Domande di pratica

Study guide - Flashcard