Question 1

Which of the following best explains why catalase is not consumed during the breakdown of hydrogen peroxide in the reaction $$2H_2O_2 + 	ext{Catalase} ightarrow 2H_2O + O_2$ + 	ext{Catalase}$$?

Accepted Answer

Catalase is regenerated at the end of each reaction cycle, allowing it to catalyze multiple reactions.

Question 2

A student increases the concentration of catalase in a reaction mixture while keeping the substrate concentration constant. What is the expected effect on the rate of oxygen production, and why?

Accepted Answer

The rate will increase until all substrate molecules are bound, after which further increases in enzyme concentration will have no effect.

Question 3

What is the most likely outcome if the catalase enzyme is exposed to a temperature of $$100^\circC $$during the experiment?

Accepted Answer

The enzyme will denature, losing its three-dimensional structure and activity.

Question 4

During the experiment, why is it important to flick the test tube to dislodge gas bubbles from the side?

Accepted Answer

To ensure accurate measurement of oxygen gas production, preventing bubbles from adhering and reducing pressure readings.

Question 5

If the pH of the reaction mixture is changed from 7 to 3, what is the most likely effect on catalase activity, and why?

Accepted Answer

Catalase activity will decrease because extreme pH disrupts the enzyme's active site.

Question 6

A researcher adds EDTA to a catalase reaction. What is the primary effect of EDTA on catalase activity, and what is the mechanism?

Accepted Answer

EDTA acts as an inhibitor by binding metal ions required for catalase activity, reducing the reaction rate.

Question 7

Which of the following best describes enzyme saturation in the context of the catalase experiment?

Accepted Answer

All active sites of catalase molecules are occupied by substrate, so increasing substrate concentration further does not increase the reaction rate.

Question 8

Suppose you increase the hydrogen peroxide concentration from 3% to 20% in the catalase reaction. What is the most likely outcome, assuming enzyme concentration remains constant?

Accepted Answer

The reaction rate will increase until the enzyme becomes saturated, after which further increases in substrate will not affect the rate.

Question 9

Why is an intermediate salt concentration, such as 0.9% NaCl, optimal for most enzymes?

Accepted Answer

It maintains proper ionic interactions among charged amino acid side chains, preserving enzyme structure and function.

Question 10

A student observes that catalase activity is highest at $$37^\circC $$and much lower at $$4^\circC $$and $$100^\circC. $$What is the best explanation for this observation?

Accepted Answer

Enzyme activity increases with temperature up to an optimum, but decreases at higher temperatures due to denaturation.

Question 11

Which of the following statements about enzyme inhibitors is correct, based on the catalase experiment with EDTA?

Accepted Answer

Inhibitors decrease enzyme activity by interfering with the active site or essential cofactors.

Question 12

If you plot enzyme concentration (x-axis) versus reaction rate (y-axis), what general shape would you expect the graph to have, and why?

Accepted Answer

A linear increase at low concentrations, leveling off as substrate becomes limiting.

Question 13

Which of the following best explains why catalase is abundant in plant storage organs such as potato tubers?

Accepted Answer

To rapidly break down hydrogen peroxide, preventing oxidative damage to stored tissues.

Question 14

A student accidentally uses a buffer with pH 12 in the catalase reaction. What is the most likely effect on the enzyme's activity?

Accepted Answer

Catalase activity will decrease significantly due to denaturation at high pH.

Question 15

Which of the following is a correct interpretation of the slope ($$m) in $$the equation $$y = mx + b$$ when plotting pressure (kPa) versus time (s) in the catalase experiment?

Accepted Answer

The slope $$m$$ represents the rate of oxygen gas production, which is a proxy for enzyme activity.

Question 16

Why is it necessary to pre-incubate the reaction mixtures at the desired temperature before starting the catalase reaction?

Accepted Answer

To ensure that the enzyme and substrate reach the target temperature, allowing accurate measurement of temperature effects on activity.

Question 17

Which of the following best describes the role of the active site in catalase function?

Accepted Answer

It provides a specific three-dimensional environment where only hydrogen peroxide can bind and be converted to products.

Question 18

A patient is poisoned with potassium cyanide, which is known to inhibit critical enzymes. Based on your knowledge of enzyme inhibition, what is the most likely mechanism by which cyanide acts?

Accepted Answer

Cyanide binds to the active site or essential cofactors of enzymes, preventing substrate binding and enzyme function.

Question 19

If a detergent is accidentally added to the catalase reaction mixture, what is the most likely effect on enzyme activity?

Accepted Answer

The detergent will act as an inhibitor by unfolding the enzyme, decreasing its activity.

Enzyme Activity: Catalase Lab Study Guide

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