Enzyme Activity Lab

Name: ______Hr: ______

Enzyme Activity Lab

Background Information:

What would happen to your cells if they made a poisonous chemical? You might think 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.

The reaction is as follows: 2H2O2 à 2H2O + 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. In this lab, you will study the catalase found in liver cells. You will be using chicken or beef liver. It might seem strange because when a cell dies, the enzymes remain intact and active for several weeks, as long as the tissue is kept refrigerated.

PREDICTIONS:

You are going to mix different tissues with hydrogen peroxide. You are going to do this to see which tissues contain catalase.

1)  What do you expect to see if catalase is present, and mixed with the hydrogen peroxide? Describe.

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2)  What do you expect to see if catalase is NOT present, and the tissue is mixed with hydrogen peroxide? Describe.

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3)  Do you think both animal and plant tissues contain catalase? Explain your reasoning.

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PART 1: DEMONSTRATION WITH LIVER

Procedure-A:

-  2mL of hydrogen peroxide is added to a clean test tube.

-  A small piece of liver is added to the test tube, and stirred.

-  Record observations in detail.

Observations-A:

1)  What do you see happening? Be as descriptive as possible.

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2)  What gas is being released? How do you know?

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3)  Does the test tube feel warmer or cooler? [Endothermic reactions absorb heat and feel cool, Exothermic reactions release heat and feel warm.]

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Procedure-B:

-  Remove the liquid remaining from Procedure-A.

-  Test the liquid removed from Procedure-A.

-  Add another 2mL of hydrogen peroxide to the liver remaining from Procedure-A.

-  Record observations in detail.

Observations-B:

1)  What was the liquid removed in Procedure-B? How do you know?

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2)  What happened when you added MORE hydrogen peroxide, to the already used liver from Procedure-A?

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3)  Is catalase reusable? Explain.

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PART 2: DEMONSTRATION WITH LIVER & HOT BATH

Procedure:

-  Add a small piece of liver to a clean test tube.

-  Add 5-10mL of distilled water to the same test tube.

-  Place the liver-tube in a hot water bath for 5minutes.

-  Remove the liver-tube from the hot water bath, and drain out the water.

-  Add 2mL of hydrogen peroxide to the test tube.

-  Record observations in detail.

Observations:

1)  Compare the liver-hydrogen peroxide reaction in Part 2, to the reactions seen in Part 1. Which seemed more vigorous and fast? Which seemed slower and less bubbly?

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2)  Why do you think there was a difference in the catalase reactions in Part 1 and Part 2?

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3)  What do you think would happen if we had placed the liver in an ice-bath? Explain.

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4)  How does temperature effect enzymes? Explain.

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PART 3: STUDENTS TEST OUT DIFFERENT TISSUES

Procedure:

-  You should have 4 test tubes at your station.

-  Measure & Pour 2mL of hydrogen peroxide into each test tube.

-  In one test tube place a small piece of potato. Record your observations in detail.

-  In one test tube place a small piece of apple. Record your observations in detail.

-  In one test tube place a small piece of chicken. Record your observations in detail.

-  In one test tube place a small piece of beef. Record your observations in detail.

Observations:

What did you see? / Was the reaction Slower or Faster than the liver? / Was Catalase present?
Yes or No. / Rank each food by their amount of Catalase.
1= little, 4 = lots
Potato / Slower Faster / Yes No / 1 2 3 4
Apple / Slower Faster / Yes No / 1 2 3 4
Chicken / Slower Faster / Yes No / 1 2 3 4
Beef / Slower Faster / Yes No / 1 2 3 4

CONCLUDING QUESTIONS:

1)  What are enzymes? What do they do in chemical reactions?

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2)  What is catalase? What does it do chemically?

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3)  How can temperature changes effect the enzymes in your body? Explain.

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