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 2H2O + O2[KR1]
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[KR2]:
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[KR3].
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2)What gas is being released? How do you know[KR4]?
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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[KR5].]
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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[KR6]?
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2)What happened when you added MORE hydrogen peroxide, to the already used liver from Procedure-A[KR7]?
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3)Is catalase reusable? Explain[KR8].
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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[KR9]?
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2)Why do you think there was a difference in the catalase reactions in Part 1 and Part 2[KR10]?
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3)What do you think would happen if we had placed the liver in an ice-bath? Explain[KR11].
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4)How does temperature effect enzymes? Explain[KR12].
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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[KR13]?
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2)What is catalase? What does it do chemically[KR14]?
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3)How can temperature changes effect the enzymes in your body? Explain[KR15].
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[KR1]This reaction says that hydrogen peroxide breaks down into liquid water, and oxygen gas. The enzyme catalse (found in liver) speeds up this reaction, so that the hydrogen peroxide breaks down SUPER FAST!
[KR2]These are your own predictions. This needs to be completed on your own!
[KR3]There was lots of white bubbles/foam, and a clear liquid forming at the bottom (where the liver was).
[KR4]We know that oxygen gas was being released because when hydrogen peroxide breaks down, it releases water and oxygen gas.
[KR5]The test tube felt hot! This is because energy (heat) is released when the hydrogen peroxide bonds are broken!
[KR6]The liquid removed was plain old water. We know because when we dropped in more liver, there was no bubbling or anything. If the clear liquid had been hydrogen peroxide, we would expect to see bubbling and foaming!
[KR7]Even after we already used the liver and its catalase, there was still tons of foaming! This is because the enzyme was still usable in the liver!
[KR8]Yes, enzymes are always reusuable unless they are degraded with heat. This means that all enzymes can be recycled. They do not change during chemical reactions at all!
[KR9]The cooked liver caused much less of a reaction, and we saw very little-no bubbling.
[KR10]There was a difference because we heated the liver up and messed with the structure of the catalse.
[KR11]This is another extreme temperature change, and it might ruin the enzymes also.
[KR12]Temperature changes the structure of the enzyme (the way it is folded). Enzymes function by the way they are folded, so it keeps them from working properly!
[KR13]Enzymes are a type of protein that speed up chemical reactions by decreasing the activation energy.
[KR14]Catalase is a type of enzyme that speeds up the breaking down of hydrogen peroxide into water and oxygen gas.
[KR15]Temperature can change the structure, and so the function of enzymes.