Enzyme Lab Report

Enzyme Lab Report

Can Catalase Be Destroyed?

AP Biology, Mod 19

Abstract. The theory that catalase can be destroyed was tested in a lab setting using the procedures provided by Mrs. Wootton. We examined this through the use of Hydrogen Peroxide in its reaction with the catalase. The catalase found in chicken liver did react. The catalase, or lack thereof, in apples and potatoes was not as readily observable. Also, after superheating and supercooling the liver, we found that the reaction with the Hydrogen Peroxide was diminished. These data suggest that catalase can be destroyed.

Introduction

In this lab, we explore the true functions of enzymes. How they break down poisonous chemicals into harmless substances.  Enzymes are proteins that speed up the rate of reactions that would happen at a slower rate with the absence of these enzymes. In enzymatic reactions, the molecules at the beginning of the process are called substrates, and the enzyme converts them into different molecules, the products. Almost all processes in a biological cell need enzymes to occur at significant rates. Since enzymes are selective for their substrates and speed up only a few reactions from among many possibilities, the set of enzymes made in a cell determines which metabolic pathways occur in that cell.Enzymes are found in many part of the cells. Enzymes work by lowering the activation energy for a reaction, thus dramatically increasing the rate of the reaction.

In this lab, we are dealing with the enzyme that is usually found in the cells of many living tissues. The name of this enzyme is catalase; it speeds up a reaction which breaks down hydrogen peroxide, a toxic chemical, into 2 harmless substances -- water and oxygen. Hydrogen peroxide is produced as a byproduct of many normal cellular reactions. In this lab we studied the catalase found in liver cells.

      

Methods

PART A - Observe Normal Catalase Reaction

1. Place 2 ml of the 3% hydrogen peroxide solution into a clean test tube.

2. Using forceps and scissors cut a small piece of liver and add it to the test tube. Push it into the hydrogen peroxide with a stirring rod. Observe the bubbles.  What gas is being released? ______________________

Throughout this investigation you will estimate the rate of the reaction (how rapidly the solution bubbles) on a scale of 0-5

(0=no reaction, 1=slow, ..... 5= very fast). Assume that the reaction in step 2 proceeded at a rate of "4"

Recall that a reaction that absorbs heat is endothermic; a reaction that gives off heat is exothermic. Now, feel the temperature of the test tube with your hand. Has it gotten warmer or colder _____________________

                                                                         Is the reaction endothermic or exothermic? _____________________

Is Catalase Reusable?

3. Pour off the liquid into a second test tube. Assuming the reaction is complete. What is this liquid composed of? _______

What do you think would happen if you added more liver to this liquid? _____________________

Test this and record the reaction rate.                                                 Reaction Rate ___________  (1 – 5)

4.  Add another 2 ml of hydrogen peroxide to the liver remaining in the first test tube.       What is the reaction rate? ________

Is catalase reusable? Explain.  ________________________________________________________________________

Part B - What Tissues Contain Catalase

You will now test for the presence of catalase in tissues other than liver. Place 2 ml of hydrogen peroxide in each of 3 clean test tubes and then add each of the three test substances to the tubes.  As you add each test substance, record the reaction rate (0-5) for each tube.

Substance	Rate of Reaction (0-5)
Potato
Apple
Chicken

Which tissues contained catalase?  _______________________________________________

Do some contain more catalase than others? How can you tell? _____________________________________________

PART C - What is the Effect of Temperature on Catalase Activity?

1. Put a piece of liver into the bottom of a clean test tube and cover it with a small amount of water. Place this test tube in a boiling water bath for 5 minutes. What will boiling do to an enzyme?  _________________________________________

2. Remove the test tube from the hot water bath, allow it to air cool, then pour out the water. Add 2 ml of hydrogen peroxide. CAUTION: Use a test-tube holder for hot test tubes.    What is the reaction rate for the boiled liver and peroxide? __________

3. Put equal quantities of liver into 2 clean test tubes and 1 ml H2O2 into 2 other test tubes. Put one test tube of liver and one of H2O2 into each of the following water baths: Ice bath and Warm water bath (not boiling).

After 3 minutes, pour each tube of H2O2 into the corresponding tube of liver and observe the reaction

What is the reaction rate for the cold liver/peroxide? ______

What is the reaction rate for the warm liver/peroxide? ______

PART D - What is the Effect of pH on Catalase Activity

1. Add 2 ml hydrogen peroxide to each of 5 clean test tubes.  

Tube 1--add 3 drops of HCl (acid)   Tube 2 - dilute HCl  (1 drop / 3 ml) – add 3 drops *Use pH paper to determine the exact pH

Tube 3 – add 3 drops of NaOH (Base) Tube 4 – dilute NaOH (1 drop / 3 ml )  - add 3 drops Tube 5 – add 3 drops of water (neutral)

Now add liver to each of the test tubes (best to do it all at the same time so reaction rates can be observed at the same time)

Rate of Reaction for  Strong Acid _____ Acid _____ Neutral ______Strong Base_____  Basic _____

*If needed you can raise your rating scale to 6

What is the optimal pH for catalase (estimate)?  _____________________________________________

Results

PART A - Observe Normal Catalase Reaction

1. Place 2 ml of the 3% hydrogen peroxide solution into a clean test tube.

2. Using forceps and scissors cut a small piece of liver and add it to the test tube. Push it into the hydrogen peroxide with a stirring rod. Observe the bubbles.  What gas is being released? Oxygen

Throughout this investigation you will estimate the rate of the reaction (how rapidly the solution bubbles) on a scale of 0-5

(0=no reaction, 1=slow, ..... 5= very fast). Assume that the reaction in step 2 proceeded at a rate of "4"

Recall that a reaction that absorbs heat is endothermic; a reaction that gives off heat is exothermic. Now, feel the temperature of the test tube with your hand. Has it gotten warmer or colder? Warmer

Is the reaction endothermic or exothermic? Exothermic

Is Catalase Reusable? Yes, it is

3. Pour off the liquid into a second test tube. Assuming the reaction is complete. What is this liquid composed of? Water

What do you think would happen if you added more liver to this liquid? Nothing, because it is just water

Test this and record the reaction rate.                                                 Reaction Rate: 0

4.  Add another 2 ml of hydrogen peroxide to the liver remaining in the first test tube.       What is the reaction rate? 5

Is catalase reusable? Explain.  Yes, because the liver juice was reused, and there was no reaction. Hydrogen Peroxide was added to the old liver, and a reaction took place

Part B - What Tissues Contain Catalase

You will now test for the presence of catalase in tissues other than liver. Place 2 ml of hydrogen peroxide in each of 3 clean test tubes and then add each of the three test substances to the tubes.  As you add each test substance, record the reaction rate (0-5) for each tube.

Substance	Rate of Reaction (0-5)
Potato	2
Apple	1
Chicken	5

Which tissues contained catalase?  Technically all.

Do some contain more catalase than others? How can you tell? Yes, because they all reacted.

PART C - What is the Effect of Temperature on Catalase Activity?

1. Put a piece of liver into the bottom of a clean test tube and cover it with a small amount of water. Place this test tube in a boiling water bath for 5 minutes. What will boiling do to an enzyme?  Denature it

2. Remove the test tube from the hot water bath, allow it to air cool, then pour out the water. Add 2 ml of hydrogen peroxide. CAUTION: Use a test-tube holder for hot test tubes.    What is the reaction rate for the boiled liver and peroxide? 0

3. Put equal quantities of liver into 2 clean test tubes and 1 ml H2O2 into 2 other test tubes. Put one test tube of liver and one of H2O2 into each of the following water baths: Ice bath and Warm water bath (not boiling).

After 3 minutes, pour each tube of H2O2 into the corresponding tube of liver and observe the reaction

What is the reaction rate for the cold liver/peroxide? 2

What is the reaction rate for the warm liver/peroxide? 2

PART D - What is the Effect of pH on Catalase Activity

1. Add 2 ml hydrogen peroxide to each of 5 clean test tubes.  

Tube 1--add 3 drops of HCl (acid)   Tube 2 - dilute HCl  (1 drop / 3 ml) – add 3 drops *Use pH paper to determine the exact pH	Tube 3 – add 3 drops of NaOH (Base) Tube 4 – dilute NaOH (1 drop / 3 ml )  - add 3 drops Tube 5 – add 3 drops of water (neutral)
TUBE 1 : 1 Tube 2pH:2 Tube 3 pH: 11 Tube 4pH: 9 Tube5pH:  7

Now add liver to each of the test tubes (best to do it all at the same time so reaction rates can be observed at the same time)

Rate of Reaction for  Strong Acid 2 Acid 4 Neutral 6 Strong Base 4 Basic 3

*If needed you can raise your rating scale to 6

What is the optimal pH for catalase (estimate)?  7

Discussion

In this lab, we observed a normal catalase reaction, what tissues contain catalase, and what is the effect of temperature on catalase activity. Observing a normal catalase reaction, we found out that adding catalase to hydrogen peroxide will lead to the release of oxygen in H2O2 leaving us with water. Adding the catalase into the hydrogen peroxide we noticed that the test tube got warmer which makes the reaction exothermic. After the reaction has taken place we found out that catalase is not reusable and the hydrogen peroxide is now just water. The second part of the lab we tested out different substances such as potato, apple, and chicken to see if they contained catalase and how great of a reaction they would have with hydrogen peroxide. We found out that all 3 of the substances contained catalase and to tell which one had the greater amount of catalase was simple to see which one had more bubbles. The last part of the lab we experimented with different temperatures on the catalase to see if it would affect the reaction. We first boiled the catalase to see what the boiling would do to an enzyme, our result was that the boiling denatured it, making it not work anymore. Our last experiment we did was testing one in an ice cold bath and another in a warm bath for a couple of minutes. The reaction rate for the cold bath made the reaction rate 2 out of 5 because it cooled it down slowing the reaction rate down. The warm bath’s reaction rate was similar to the cold bath making the reaction rate of 2 out of 5.

Conclusion

The purpose of this lab was to see how catalase from different hosts reacted in different environments. We learned that the catalase found in chicken liver reacted less when cooled, and not at all when heated. There was little catalase at all in the apples and potatoes. The catalase was destroyed in the heating phase, as the liver changed its chemical composition. The optimal ph for catalase is neutral, because that it what most of the body is comprised of. The optimal temperature of catalse is 98.6 degrees Fahrenheit, because that is the average temperature of the human body.