Catalase Lab:

Observing the Rate of Reaction and Investigating the Effect of Environmental Variables

 

Introduction

Enzymes catalyze reactions in your body. The function of an enzyme depends on it shape. ItŐs shape is determined by bonds within the protein and between different sections of the protein. These bonds can be affected by the environmental conditions the enzyme is in. Hydrogen peroxide is created in our bodies and is harmful and needs to be removed. The decomposition of hydrogen peroxide (H2O2) into water and oxygen is a reaction that happens in your cells. It is catalyzed by an enzyme called catalase.  The overall reaction is:

 

2H2O2 --- > 2H2O + O2

 

In this lab, you will first make a measure of the time it takes for this reaction to occur.  Next, you will investigate the effect of a variable on the time it takes for the reaction to occur. In your discussion think about how the changes you have made affect the enzyme and the rate of the reaction.

 

Prelab

Your prelab should include the following:  title/date, purpose (2 -4 sentences. do alittle research to find out why hydrogne peroxide is made in our bodies and why it needs to be removed) , cut and paste procedure from this sheet (for parts I and II), and data table (for part I and part II).

 

Procedure, Part I

1.            Place 5mL of 3% hydrogen peroxide solution in a test tube.

2.            Using forceps, dip a filter paper disc in the catalase extract solution; gently shake to remove excess solution.

3.            Drop the filter paper into the test tube, trying to prevent the disc from sticking to the side of the tube.  Immediately begin timing.

4.            Record the time taken for the disc to rise to the top of the solution.

5.            Repeat steps 1-4 two additional times.  Each time, discard the previously used hydrogen peroxide solution into the waste beaker and replace with 5mL of new peroxide solution.

 

Procedure, Part II

Your teacher will tell you which of the following three procedures your group will perform.  However, you should read all three so that you are familiar with what your classmates are doing.

 

A.            Effect of pH

1.            Mix 1mL of catalase solution with 1mL of the acid solution provided.  Mix 1mL of catalase solution with 1mL of  the base  solution provided.  Let these mixtures sit for 3-5 minutes.

2.            Perform steps 2-5 according to the instructions in part I for both catalase solutions.

 

B.            Effect of temperature

1.            Place 5mL of catalase solution into an ice bath for 3 minutes.  Place another 5mL of catalase solution into the          boiling water bath for 3 minutes.

2.            Perform steps 2-5 according to the instructions in part I for both catalase solutions.

 

C.           Effect of substrate concentration

 

1.            Perform steps 1-5 according to the instructions in part I, making the following changes.

               a.            Use a 1.5% hydrogen peroxide solution.

               b.            Use a 0.75% hydrogen peroxide solution.

 

Class Results

Make a labelled data table in which you record the data collected by not only yourself but your classmates as well (for Procedure, Part I & II).  In addition to all raw data, you should calculate averages for each treatment.

 

Discussion

1. What did you learn about the effects of each of the three variables investigated?  How do you explain the effect of each?

 

2. While the title of this investigation states that you will be observing the rate of a reaction, what you measured was not actually a rate.  Explain this.

 

3.Why do you need to replace the hydrogen peroxide at the beginning of each new trial?

 

4.Identify four limitations or errors in the procedure.  For each, explain how the quality of the data collected is affected.  You can refer to either part of the procedure.

Scoring of Lab Report

 

Pre-lab

 

Title/date (1)

 

purpose  (5)

 

 

Data table  (5)

 

 

Post-lab

 

 Discussion

 

Total points: 25