DO NOW:

Read the paragraph below. Answer the following questions:

What are enzymes and what is their function?

 

 

 

INTRODUCTION

Metabolism is the sum total of chemical reactions in the body that are necessary to the maintenance of life. Enzymes are biological catalysts that can speed up and control chemical reactions that would otherwise virtually never occur at normal body temperature, 37°C (98.6°F). Thousands of chemical reactions are occurring in the human body every moment of life, and a particular enzyme controls each of these reactions.

 

Enzymes are extremely efficient. Some of the chemical reactions that take place in the body produce toxic by-products such as hydrogen peroxide (H2O2). Hydrogen peroxide (H2O2) is a poisonous byproduct of metabolism that can damage cells if it is not removed. Metabolism is chemical reactions that occur in living organisms that are necessary to maintain life. Catalase is an enzyme that speeds up the breakdown of hydrogen peroxide into water (H2O) and oxygen gas (O2). 

                                                                            

                                                          H2O2 ---------------------> H2O + O2

 

REMEMBER: A CATALYST is a substance that lowers the activation energy required for a chemical reaction, and therefore increases the rate of the reaction without being used up in the process.

CATALASE is an enzyme, a biological (organic) catalyst. Hydrogen peroxide is the substrate for catalase.

 

 

YOU WILL BE WORKING WITH HOT WATER, ACIDS, AND BASES IN THIS LABORATORY. USE EXTREME CAUTION AND WEAR GOGGLES AT ALL TIMES!!!

 

Materials:

Reaction chamber

10 ml graduated cylinder

Thermometer

50 ml graduated cylinder

 Stopwatch

Data Table

3 ml syringe

1 bottle hydrogen peroxide

Paper Towels

Water bath (about 5cm water)

10 ml catalase solution in a small Beaker

 

 

 

Procedure:

                    Fill water bath with tap water up to about 8cm.

                    Obtain a reaction chamber, take off the top, and place 10 mL of hydrogen peroxide.
                    (Use a small graduated cylinder to measure out the hydrogen peroxide.)

                    In a syringe, take 1mL of catalase.

                    Fill a 50 mL graduated cylinder with water and invert in bath so water doesn’t come out.

                    BE QUICK WITH THIS STEP: Add the catalase in the syringe to hydrogen peroxide in the 
                    chamber and quickly put in stopper and place spout under opening of the graduated  

                    cylinder in the water bath.  Start your stopwatch!

                    Collect bubbles of O2.  Every 20 seconds, record the amount of oxygen in the graduated cylinder.  

                    Record your data in the data table under “Tap Water”.

                    Continue recording for 300 seconds.  Be sure to record a reading every 20 seconds.

                    Repeat the experiment using a different experimental condition and record your data in the data

                    table.

 

 

 

Experimental Conditions:

Manipulate experimental conditions:

 

                  Warm up hydrogen peroxide to (32o-37o C).

                 Heat the hydrogen peroxide to 100oC.

                 Allow hydrogen peroxide to sit in an ice water bath (5-8o C).

                 Change the concentration of catalase enzyme used. Use 2 mL of catalase.

                 Change the concentration of hydrogen peroxide. Use 20 mL of hydrogen peroxide.

                 Alter the pH of the reaction by adding acid. Add 5 drops of acid.

                 Alter the pH of the reaction by adding base. Add 5 drops of base.

 

 

 

Plan:

Each group will investigate and report on their findings.

EVERY STUDENT IS RESPONSIBLE FOR RECORDING THE RESULTS OF ALL EXPERIMENTS on his/her paper.
 

                                                                                                  Data Table

 

 

 

 

 

 

 

Amount of Oxygen Collected (mL)

 

 

 

 

 

 

 

 

 

 

                                                                                                            Time (Seconds)

Tap Water

 

Warm Water Bath

32o-37o C

Boiling Water Bath

100oC

Ice Water Bath

5-8o C

2 mL of catalase

20 mL of hydrogen peroxide

Add 5 drops of acid

Add 5 drops of base

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Presentation of Results: Line Graph

Create a line graph on a computer showing time (seconds) on the x-axis and oxygen collected (mL) on the y-axis. Title of graph is “Rate of Breakdown of Peroxide with Catalase”. Your graph must be easy to read and it must make sense. 

Make sure you:

Use different colors to show different experimental conditions.Have a key.Label the axes and have the title.Show clear data points. 

Use an appropriate scale for the data such that the presentation looks neat. Draw single, clear, best-fit lines.

 

 

Post-Lab Questions: (Complete for Homework)

After completion of the lab and making your graph, answer the following questions on the back of your graph or on a separate sheet of paper.

  • What experimental condition was the control? What were the variables in this experiment?

 

 

 

  • Write the balanced equation that shows the decomposition of hydrogen peroxide.

 

 

  • How does concentration of enzyme affect the rate of reaction?

 

 

 

  • How does the concentration of substrate affect the rate of reaction?

 

 

 

  • How does temperature affect the rate of reaction?

 

 

 

  • How does pH affect the rate reaction?

 

 

 

  • If you wanted to make catalase break down hydrogen peroxide as quickly as possible, what conditions would you provide for the reaction?

 

 

 

 

When you increase the enzyme concentration, the reaction rate changes.

How does the reaction rate change?

 

 

  • Explain this change in terms of the number of molecules present in the reaction. In order words, what is going on at the molecular level to cause the rate to change in that way?

 

 

 

  • Explain in terms of kinetic energy why it is that increasing the temperature of the reaction caused the changes in reaction rate you observed.

 

 

 

 

  • If you were to heat up catalase to 100oC and then add it to hydrogen peroxide, what would you expect to happen to the reaction rate?  Explain your answer clearly in terms of protein structure.

Catalase