Skip to Main Content
It looks like you're using Internet Explorer 11 or older. This website works best with modern browsers such as the latest versions of Chrome, Firefox, Safari, and Edge. If you continue with this browser, you may see unexpected results.
site header image

Biofuels Webquest: Tiny Bubbles

Tiny Bubbles

Why do some people put "Hydrogen peroxide" H2O2 on their cuts? 

Ready:


What are these tiny bubbles and why do people care? How could you identify these unknown tiny bubbles?

 

1.   Place 15 ml of hydrogen peroxide into a small beaker. 

 2.  Using Scissors, cut a small piece of liver approximately the size of a small sugar cube.  Place it into the beaker with the hydrogen peroxide.

 3.   Light a wooden splint with a match and extinguish it by blowing it out leaving a glowing splint. Place the glowing splint into the beaker by holding it firmly in place.

 4.   Explain what is happening.  What gas makes these tiny bubbles and how do you know based on what you just did? 

SET: 

Watch this video

An enzyme catalyzes a chemical reaction, causing substrates to react to form products.  Within living systems a wide variety of chemical reactions takes place.  Reaction rates of chemical processes within an organism are greatly accelerated by enzymes.  Since enzymes are catalysts, they can affect only the rate of a reaction.  They cannot cause the formation of more product than would be generated without the enzyme.

Enzymes are not consumed while speeding up a reaction.  They act by combining, for only an instant, with the reactant or substrate.  When the product is formed, the enzyme is released to combine with other substrate molecules.

All enzymes are proteins.  The specificity of the enzyme is determined by the shape of the active site, the portion of the enzyme that binds the substrate and causes the chemical reaction.  All the factors, such as temperature and pH that can affect the shape of a protein will also influence its enzymatic activity.

In our cells many reactions produce as a product

"Hydrogen peroxide" H2O2

What would happen to your cells if they made a poisonous chemical? You might think that they would die.  In fact, your cells are always making poisonous chemicals. They do not die because your cells use enzymes to break down these poisonous chemicals into harmless substances.  Enzymes are proteins that speed up the rate of reactions that would otherwise happen more slowly.  The enzyme is not altered by the reaction.  You have hundreds of different enzymes in each of your cells.  Each of these enzymes is responsible for one particular reaction that occurs in the cell. 

 

                                                                                (catalase)

2 H2O2 -------------------->  2 H2O  +  O2

GO:

The purpose of this experiment is to demonstrate some of the interesting properties of enzymes, and to show how enzymatic reactions differ from ordinary nonenzymatic chemical reactions.

In this lab, you will study an enzyme that is found in the cells of many living tissues.  The name of the enzyme is catalase; it speeds up a reaction which breaks down hydrogen peroxide, a toxic chemical, into 2 harmless substances -- water and oxygen.  The reaction is as follows:

2 H2O2 ----------------> 2 H2O  +  O2

This reaction is important to cells because hydrogen peroxide (H2O2) is produced as a byproduct of many normal cellular reactions.  If the cells did not break down the hydrogen peroxide, they would be poisoned and die.

We will be using chicken liver.  It might seem strange to use dead cells to study the function of enzymes.  This is possible because when a cell dies, the enzymes remain intact and active for several weeks, as long as the tissue is kept refrigerated.  You will describe the effects of changes in temperature and pH on the activity of enzymes.   You should at the end understand that enzymes are proteins which can be reused over and over again and do not actually participate in the chemical reaction.

PROCEDURE: 

 

Part A

Effect of Temperature on Catalase Activity


@ room temperature

( how rapidly the solution bubbles) on a scale of O to 5 (O = no reaction,

1.   Place 15 ml. of hydrogen peroxide into a clean small beaker. 

2.     Using forceps and scissors, cut a small piece of liver approximately

the size of a small sugar cube.  Place it into a clean small beaker with the hydrogen peroxide.

3.   Observe the gas bubbles and estimate the rate of the reaction 

(how rapidly the solution bubbles) on a scale of O to 5 (O = no reaction)

 1 = slow, ..., 5 = very fast).

 4.   Record the rate of this reaction at room temperature on your data

 table.

 

@ Hot temperature

 

             1.     Place a piece of liver into the bottom of the clean test tube and cover

 it with a small amount of water (about 1/3 of a test tube).  Place this test tube into a boiling water bath for 5 minutes.

            2.    Remove the test tube from the hot water bath, allow it to air cool, then pour out the water. 

 3.      Add 15 ml. of hydrogen peroxide into a clean small beaker.  Then place the "boiled liver" from above into the small beaker with the hydrogen peroxide.

 

            4.    Record the rate of enzyme activity in your data table.

 

@ Cold temperature

 

            1.    Place a piece of liver into the bottom of the clean test tube and cover

it with a small amount of water (about 1/3 of a test tube).  Place this test tube into a ice water bath for 5 minutes.  Also add 15 ml. of hydrogen peroxide into a clean small beaker and place it into the ice Bath to cool the hydrogen peroxide down.

2.  Remove the test tube from the ice bath, and then pour out the water.  Then place the cold liver into the beaker with the cold hydrogen peroxide.

           3.    Record the rate of enzyme activity in your data table.


@ Warm temperature ( body temp. )

 

                  1.     Place a piece of liver into the bottom of the clean test tube and cover it with a small amount of water.  Place this test tube into a warm water bath (warm water bath (37oC) ) for 5 minutes.  Also add 15 ml. of hydrogen peroxide into a clean small beaker and place it into the warm Bath to warm the hydrogen peroxide up.

 

                  2.    Remove the test tube from the warm water bath and

then pour out the water.  Then place the warm liver into the beaker with the warm hydrogen peroxide

 

3.     Record the rate of enzyme activity in your data table.

 

Part B

 

Is catalase reusable?

1.                  Place 15 ml. of hydrogen peroxide into a clean small beaker. 

2.                  Using forceps and scissors, cut a small piece of liver                                                                  approximately the size of a small sugar cube. 

  Place it into a clean small beaker with the hydrogen peroxide.

 

3.                  Pour the liquid out into your sink after letting it sit for 5 minutes.

                 

4.                  Add another 15 ml. of hydrogen peroxide to the liver remaining in the beaker.  Record results in your table.

 

Part C

 

The Effect of low pH (Acid ) and high pH ( Base ) on Catalase Activity

CAUTION:  Do not let acid or Base contact your skin. 

 

ACID

 

1.                  Place 15 ml. of hydrogen peroxide into a clean small beaker.  Also add

                                    5.0 ml. of Acid into the beaker.

 

                                    (After adding the acid measure the pH with pH paper.) 

 

                  2.                  Place a small piece of liver into a clean small beaker with the hydrogen peroxide.

 

                  3.                  Record the rate of this reaction on your data table.

 

BASE

 

                  1.   Place 15 ml. of hydrogen peroxide into a clean small beaker.  Also add

 5.0 ml. of Base into the beaker.

 

                                    (After adding the base measure the pH with pH paper.) 

 

                  2.   Place a small piece of liver into a clean small beaker with the hydrogen peroxide.

 

                  3.    Record the rate of this reaction on your data table.

 

RESULTS

 1.     Include data table

 2.    Include 2 bar graphs.  One graph should indicate the rate of enzyme activity (Y-axis) over the varying temperatures (X-axis) and the other graph should  indicate the rate of enzyme activity vs. pH.

 

 

ANALYSIS OF RESULTS

 

Watch this you tube video and explain the biology of enzymes in these demos, (not so tiny bubbles!).

1.                  In the reaction that you are studying in this lab, what is the enzyme?

                     What is the substrate?  What are the products?

 

2.                  Are enzymes reusable?  Explain and cite results from this lab to

                       support your explanation.

 

3.                  What will boiling do to an enzyme?  Explain and cite results from

                      this lab to support your explanation.

 

4.                  What is the effect of various temperatures on enzyme activity?

                      Explain and cite results from this lab  to support your explanation.

                       What is the optimum temperature for catalase?

 

5.                  What is the effect of various pHs on enzyme activity?  Explain and

                      cite results from this lab to support your explanation.  What is the

                      optimum pH for enzyme catalase?

 

6.                  Compare optimal temperature and optimal pH for catalase to the conditions of a cell.

Subject Guide

Profile Photo
Jennifer Jourdain
Contact:
Montachusett Regional Voc Tech School
1050 Westminster Street
Fitchburg, MA 01420
jourdain-jennifer@montytech.net
(978) 345-9200 x5125
Website