Question 1

Which of the following best describes the primary function of catalase in the liver extract assay described in the experiment?

Accepted Answer

Catalase acts as a biological catalyst, reducing the activation energy required for the decomposition of hydrogen peroxide into water and oxygen.

Question 2

In the catalase assay, why is it important to keep the pH constant during the reaction?

Accepted Answer

Because changes in pH can alter the conformation of catalase, affecting its ability to form enzyme-substrate complexes.

Question 3

If you were to plot the amount of hydrogen peroxide ($$\mathrm{H_2O_2}) $$remaining over time during the catalase reaction, what would the curve look like?

Accepted Answer

A curve that decreases rapidly at first and then levels off as the reaction proceeds.

Question 4

Which equation should you use to convert the measured volume of oxygen gas at experimental conditions to the volume at STP?

Accepted Answer

$$\frac{P_{\mathrm{Expt}} V_{\mathrm{Expt}}}{T_{\mathrm{Expt}}} = \frac{P_{\mathrm{STP}} V_{\mathrm{STP}}}{T_{\mathrm{STP}}}$$

Question 5

Why does the reaction rate of catalase tend to level off at high substrate concentrations?

Accepted Answer

The enzyme becomes saturated with substrate, so adding more substrate does not increase the rate.

Question 6

What is the most likely explanation for the decrease in reaction rate as the catalase reaction progresses?

Accepted Answer

The substrate concentration decreases, reducing the frequency of enzyme-substrate collisions.

Question 7

Which of the following best explains why catalase activity is severely reduced at very low pH (e.g., pH 3)?

Accepted Answer

The enzyme's structure is disrupted, preventing effective enzyme-substrate complex formation.

Question 8

If you stopped the catalase reaction at pH 3 and then raised the pH to 7 without adding more catalase, what would you expect to happen?

Accepted Answer

The reaction would resume and more oxygen would be produced.

Question 9

Which of the following best describes the effect of temperature on enzyme activity below the enzyme's optimum temperature?

Accepted Answer

Enzyme activity increases because molecular motion and collision frequency increase.

Question 10

What is the role of the graduated cylinder in the catalase assay setup?

Accepted Answer

To collect and measure the volume of oxygen gas produced during the reaction.

Question 11

Which of the following best defines the 'active site' of an enzyme?

Accepted Answer

The region of the enzyme where the substrate binds and the reaction occurs.

Question 12

A student forgets to subtract the initial air volume from each reading when calculating the volume of oxygen produced. What is the most likely consequence?

Accepted Answer

The calculated oxygen volumes will be too high.

Question 13

Which of the following best describes the 'induced-fit' model of enzyme action?

Accepted Answer

The enzyme changes shape slightly to better fit the substrate upon binding.

Question 14

If the tubing clamp on tube 'A' is left closed during the reaction, what is the most likely result?

Accepted Answer

Oxygen gas will not be able to enter the graduated cylinder, and the water level will not change.

Question 15

Which of the following is the correct formula for calculating the slope of the initial rate of reaction from a progress curve?

Accepted Answer

$$	ext{Slope} = \frac{Y_2$ - Y_1$}{X_2$ - X_1$}$$

Question 16

Which of the following best explains why the reaction rate decreases as the optimal temperature is exceeded?

Accepted Answer

The enzyme denatures, losing its functional shape.

Enzyme Kinetics: Catalase Assay and Factors Affecting Enzyme Activity

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