Question

Please Refer to This Lab Background:

Procedure

Only one group prepares each type of extract, and then shares the extract. Make enough for all of the groups.

1. Cut a piece of the tissue to be tested, approximately 4x4 cm.
2. Cut into smaller pieces; then grind in a mortar and pestle with a pinch of sand and 8 mL of deionized water to break the cell walls and release the catalase into solution.
3. Place the mortar and pestle on the side bench for other groups to use also.
4. Be sure to wash the mortar, pestle and dropper well when finished, using soapy water. Keep all tissue material out of the sink drain. Discard any remaining tissue material in the trash.
5. Use 1 drop (NOT 1 dropperful!) of the fluid extract in the following experiments.

Activity 1 - Comparison of catalase activity in two tissues

HYPOTHESIS: Catalase activity (as demonstrated by foam layer height) is the same in apple and potato tissues.

1. To each of the tubes below add 1 drop of tissue extract and 1 dropper (1 mL) of water:

Tube 1: apple

Tube 2: potato

2. Add 1 dropper (1 mL) of H₂O₂ to each tube and record the time.
3. After 1 min, measure the height of the foam layer in millimeters (mm).
4. Record the results and answer the questions in your laboratory report.

Wash all glassware with soapy water, rinse well and dry.

Activity 2 - Effect of temperature on catalase activity in potato

HYPOTHESIS: Temperature has no effect on catalase activity.

1. Add 1 drop of potato extract and 1 ml of water in each of four test tubes numbered 1A, 2A, 3A, and 4A.
2. Add 1 mL of H₂O₂ to each of four test tubes numbered 1B, 2B, 3B, and 4B.
3. Expose the tubes to the temperatures below for 5 minutes. Measure and record the temperature of each exposure.

Tubes 1A and 1B: in a beaker of ice water

Tubes 2A and 2B: at room temperature

Tubes 3A and 3B: in a beaker of water at 70°C

Tubes 4A and 4B: in a beaker of boiling water

4. After 5 min, pour the peroxide from tubes 1B, 2B, 3B and 4B into corresponding tubes 1A,

2A, 3A and 4A. Measure the height of the foam layer in each tube after 1 minute.

5. Record the results and answer the questions in your laboratory report.

Wash all glassware with soapy water, rinse well and dry.

Activity 3 - Effect of pH on catalase activity

HYPOTHESIS: pH has no effect on catalase activity.

1. To each of the tubes below add 1 drop of potato extract and 1 mL of buffer solution as indicated.

Tube 1: pH 2

Tube 2: pH 3

Tube 3: pH 11

2. Add 1 mL of H₂O₂ to each tube and record the time.
3. After 1 min, measure the height of the foam layer in millimeters (mm).
4. Record the results and answer the questions in your laboratory report.

Wash all glassware with soapy water, rinse well and dry.

Activity 1 - Comparison of catalase activity in two tissues

1. What is the hypothesis?____________________________________________________

2. Record the height of the foam layer after 1 min

Tube	Tissue	Thickness of Foam (mm)

3. Is the hypothesis supported by the results? _____________________________________
4. What can you conclude from your results? ___________________________________________________

________________________________________________________________________________________

________________________________________________________________________________________

________________________________________________________________________________________

Activity 2 - Effect of temperature on catalase activity in potato

1. What is the hypothesis? _______________________________________________________________________

What is the independent variable? ____________________________________________     

What is the dependent variable? ______________________________________________

2. Record the height in mm of the foam layer after 1 min.

Tube	Temperature (°C)	Thickness of Foam (mm)

3. Do your results support the hypothesis?________________

What can you conclude from your results?

4. Which temperature completely inactivated catalase?_______________________

Activity 3 - Effect of pH on catalase activity

1. State the hypothesis._________________________________________________________________________

What is the independent variable? ____________________________________________     

What is the dependent variable? ______________________________________________

2. Tube pH             Thickness of Foam (mm)

   Record your results

3. Do the results support the hypothesis?___________________ State a conclusion from your results.

4. At what pH is catalase completely inactivated?

Answer 1

The following answer is made using the biological activity of the catalase to predict results in Activity 1. The following results are the expected catalase activity in both tissues.