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Ap Biology Enzyme Lab

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AP Biology Enzyme Lab

Introduction: Hydrogen peroxide is formed as a waste product of metabolism in many living organisms. It is toxic and must be quickly converted into other, less dangerous chemicals. To manage this problem, the enzyme catalase is frequently used to rapidly catalyze the decomposition of hydrogen peroxide into harmless oxygen gas and water. Catalysis is the acceleration of a chemical reaction by means of a substance, called a catalyst that is itself not consumed by the overall reaction. Catalase has one of the highest turnover rates for all enzymes; one molecule of catalase can convert 83,000 molecules of hydrogen peroxide to water and oxygen per second.

Enzymes are biological catalysts. Enzymes are vital to such bodily functions as digestion, and they make possible processes that normally could not occur except at temperatures so high they would threaten the well-being of the body.

The catalase test is done by adding hydrogen peroxide to an organism. If bubbles form, the organism is catalase positive and if no bubbles appear, then the organism is catalase negative. In this lab experiment the reaction rate will be measure on a scale of one to five. One being the slowest reaction, five being the highest.*

In this lab I hope to learn what more about what exactly enzyme catalyze is, and the conditions it needs to work. I will be testing factors such as temperature, pH, and the enzyme concentration.

Materials: -1 molar HCI solution (in dropper bottle)

-1 molar NaOH solution (in a dropper bottle)

-6 Test tubes and Test tube holder

-10 ml Graduated cylinder

- 40 ml 3% Hydrogen peroxide solution (found in stores)

- Scissors

- Forceps

- Thermometer

- Stirring rod

- pH litmus papers

- Fresh liver, chicken meat, apple, and potato

Procedure

Part A:

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.

(See data table on page 4 for results.)

Reused 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.

3. Once the reaction has stopped, pour the liquid into another test tube.

4. Add a fresh piece of liver to the used liquid

5. Add another 2ml of hydrogen peroxide on to the used liver remaining in the first test tube.

(See data table on page 4 for results.)

Part B:

What Tissue Contain Catalase?

1. Place 2 ml of hydrogen peroxide in each of 3 clean test tubes

2. To the first test tube add a small piece of potato

3. To the second test tube add a small piece of chicken

4. To the third test tube add a small piece of apple

(See data table on page 4 for results.)

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.

2. Cover it with a small amount of distilled water.

3. Place this test tube in a boiling water bath for 5 minutes.

CAUTION: Use a test-tube holder when handling the hot test tubes.

4. Remove the test tube from the hot water bath.

5. Allow it to air cool.

6. Pour out the water.

7. Add 2 ml of hydrogen peroxide

8. Put equal quantities of liver into 2 clean test tubes

9. 1 ml H2O2 into 2 other test tubes

10. Put one test tube of liver and one of H2O2 into an ice bath

11. Put one test tube of liver and one of H2O2 into an warm water bath

12. After 3 minutes, pour each tube of H2O2 into the corresponding tube of liver

(See data table on page 5 for results.)

Part D:

What is the Effect of pH on Catalase Activity?

CAUTION: Do not let acids or bases contact your skin or clothing. Swirl each test tube after adding each drop then measure the pH of each solution. To do this, remove a drop of solution from a test tube using a clean glass stirring rod. Place the drop on pH paper. Rinse your stirring rod and wipe dry before you dip it into each test tube.

1. Add 2 ml hydrogen peroxide to each of 3 clean test tubes.

2. In one tube add one drop of HCl (acid) at a time until pH 3.

3. In the second tube add one drop of NaOH (base) at a time until pH 10.

4. In the last tube add one drop of 1molar HCl or 1molar NaOH as needed until pH 7.

(See data table on page 5 for results.)

Results

Subject Rate Reaction Observations & Conclusions

Part A Normal Liver 5 -The test tube has become warm; it is an exothermic reaction.

-There are many bubbles; I suspect the gas being let off is oxygen.

-Bubbles stopped forming quickly, the reaction was over quickly.

Liver

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