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Catalase Enzyme Lab: Investigating Enzyme Activity and Factors Affecting It, Lecture notes of Enzymes and Metabolism

In this lab, you will study the catalase found in liver cells. You will be using chicken or beef liver. It might seem strange to use dead cells to study the ...

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Catalase Enzyme Lab
Background information
Liver and other living tissues contain the enzyme catalase. This enzyme breaks down hydrogen peroxide,
which is a harmful by-product of the process of cellular respiration if it builds up in concentration in the
cells. If we use potato or other tissue containing this enzyme, we can use this to measure the relative
influence of varying several different factors on the activity of enzymes in living tissue.
In order to obtain energy and building blocks from food, the digestive system must break down proteins,
fats and carbohydrates. In this process, specific enzymes catalyze hydrolysis reactions in which food
polymers are broken up into monomers. In this lab, you will perform reactions involved in digestion of
carbohydrates, lipids, and proteins and observe the results of these reactions.
INTRODUCTION: 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. 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
(KAT-uh-LAYSS); 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: 2H2O2 ----> 2H2O + O2 (fix)
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 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.
MATERIALS:
6 Test tubes and Test tube holder
10-ml Graduated cylinder
40 ml 3% Hydrogen peroxide solution (found in
stores)
Sodium Bicarbonate
Straight-edged razor blade
Scissors and Forceps (tweezers)
Thermometer
Stirring rod
pH paper
Hydrochloric Acid
Fresh liver, chicken meat, Apple, and Potato
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Catalase Enzyme Lab

Background information Liver and other living tissues contain the enzyme catalase. This enzyme breaks down hydrogen peroxide, which is a harmful by-product of the process of cellular respiration if it builds up in concentration in the cells. If we use potato or other tissue containing this enzyme, we can use this to measure the relative influence of varying several different factors on the activity of enzymes in living tissue. In order to obtain energy and building blocks from food, the digestive system must break down proteins, fats and carbohydrates. In this process, specific enzymes catalyze hydrolysis reactions in which food polymers are broken up into monomers. In this lab, you will perform reactions involved in digestion of carbohydrates, lipids, and proteins and observe the results of these reactions. INTRODUCTION: 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. 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 (KAT-uh-LAYSS); 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: 2H 2 O 2 ----> 2H 2 O + O 2 (fix) This reaction is important to cells because hydrogen peroxide (H 2 O 2 ) 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 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. MATERIALS: 6 Test tubes and Test tube holder 10 - ml Graduated cylinder 40 ml 3% Hydrogen peroxide solution (found in stores) Sodium Bicarbonate Straight-edged razor blade Scissors and Forceps (tweezers) Thermometer Stirring rod pH paper Hydrochloric Acid Fresh liver, chicken meat, Apple, and Potato

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.
  3. 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" 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.
  4. Has it gotten warmer or colder - Is the reaction endothermic or exothermic? Is Catalase Reusable?
  5. Place 2 ml of 3% hydrogen peroxide solution into a clean test tube and add a small piece of liver. What is happening in your test tube?
  6. Pour off the liquid into a second test tube. Assuming the reaction is complete. What is this liquid composed of?
  7. What do you think would happen if you added more liver to this liquid? Test this and record the reaction rate. Explain your results (what is the liquid composed of?)
  8. Add another 2 ml of hydrogen peroxide to the liver remaining in the first test tube. Is catalase reusable?
  1. After 3 minutes, pour each tube of H 2 O 2 into the corresponding tube of liver and observe the reaction. Record the reaction rates (0-5) in DATA TABLE You recorded the reaction rate for room temperature earlier. What is the "optimum" temperature for catalase? (This is the temperature at which the reaction proceeds fastest.) Why did the reaction proceed slowly at 0 0 .C? Why did the reaction not proceed at all at 100 deg.C?

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

  1. Add 2 ml hydrogen peroxide to each of 3 pH test tubes. Treat each tube as follows: Tube 1—Has a pH 3 (ACIDIC). Add 2mL HCL Tube 2—Has a pH 10 (BASIC). Add 2mL Sodium Bicarbonate Tube 3—Has a pH 7 (NEUTRAL). Add 2 mL distilled water
  2. Add a small piece of liver to each test tube. Estimate the reaction rates (0-5) and record in DATA TABLE.
  3. Does there appear to be a pH "optimum"?
  4. At what pH?
  5. What is the effect of low or high pH on enzyme activity?

DATA TABLE

Rate of

Reaction

Observations & Conclusions (answer section questions)

PART

A

Normal Liver

Liver added to

Used Peroxide

Reused Catalase

PART

B

Potato

Chicken

Apple

PART

C

Boiled Liver

Ice Bath Liver

Warm Liver

PART

D

Basic Solution (pH

Acidic Solution

(pH 3)

Neutral Solution

(pH 7)