Investigating a factor affecting the activity of the enzyme peroxidase

The compound hydrogen peroxide (H2O2) is a by-product of metabolic reactions in most living organisms. However, hydrogen peroxide is a damaging molecule inside cells. As a result nearly all organisms produce the enzyme peroxidase, which breaks down hydrogen peroxide as it forms. Celery is one source of peroxidase. Peroxidase facilitates the breakdown of hydrogen peroxide into water and oxygen. This reaction can be detected by observing the oxygen bubbles generated.

In this lab you design a procedure and, carry out an experiment to test the effect of temperature OR substrate concentration on peroxidase activity.

There are 2 parts to this lab. In part A, you will use celery and observe the peroxidase reaction. In part B, you design a procedure and, with your teachers approval, carry out an experiment to test the effect of temperature OR substrate concentration on peroxidase activity. Only part B requires a formal lab write up which will be submitted for evaluation.

Part A: Observing the peroxidase reaction1. Put on your safety goggles. Use forceps to place a small amount of celery into a test tube.2. Use a dropper to add 2 ml of hydrogen peroxide to the test tube.3. Observe and record any evidence of a chemical reaction. Measure the maximum height of the bubbles.4. Test for the production of oxygen by performing a glowing splint test on the test tube. To do this, light a

wooden splint in the Bunsen burner flame and blow it out so that only a glowing tip remains. Then lower it into the mouth of the test tube. If bubbles are forming in the test tube, break them with the splint to test the gas inside them. Record your results.

5. The reaction in the test tube eventually stops. Does it stop because all of the hydrogen peroxide has run out or because the peroxidase has run out? To test this, take the liquid (hydrogen peroxide) from the test tube and pour it into a new test tube. Add a fresh piece of celery to the old hydrogen peroxide. Record your observations.

6. Add new hydrogen peroxide to the old celery. Record your observations7. Is peroxidase reusable? Use your data to support your answer.8. Pour the celery from the test tubes into a waste beaker, clean each of the test tubes out, and put all materials

away.

Part B: Design an experimentUsing the techniques you learned in Part A, design an experiment to test the effects of temperature OR substrate concentration on celery peroxidase. Create a research question for this experiment. Ensure that you have designed a method that controls the variables, and allows the collection of sufficient, relevant data. Present this lab as a typed report using sentence and paragraph structure. Your lab should not exceed 3 typed pages. Include only the sections mentioned below and be sure to meet the expectations of the rubric.

Introduction Include brief background information about enzymes generally and the importance of peroxidase. You will need to develop a research question

Hypothesis: Use your observations from Part A and make a prediction about how temperature OR substrate

concentration will affect the rate at which peroxidase breaks down hydrogen peroxide. Create a hypothesis to explain your prediction.

Variables: Identify the independent, dependent, and controlled variables for your lab.

Independent variable: the variable that you are studying (changing) in an experiment. It is the only variable you change.

Dependent variable: the factor which is measured in response to the change in the independent variable

Controlled variables: all the factors that are held constant in an experiment. Minimum of 5 controlled variables. Quantify each, if possible.

The best way to organize this information is to make a table with columns for the different variables.

Materials: List all the required material for the lab.

Procedure: Write the procedure as a numbered sequence. Consider these questions:

o How will you change and control your independent variable?o What variables/factors need to be controlled?o What data will you collect and in what form will you record it?o What method will you use to confirm the reaction has happened?

Be sure to include enough details in your procedure for a classmate to replicate the experiment.

Results: Organize your results in a table. Include qualitative observations. Make an appropriate graph of your results.

Conclusion and Evaluation: State a conclusion, based on an interpretation of the data. It should be justified and relate back to your

hypothesis. Evaluate at least two biological weaknesses and/or limitations of this lab and suggest realistic

improvements of the identified weaknesses and/or limitations.

Due Date: _______________________________________

Design

Levels/MarksDefining the question and

selecting variablesControlling Variables Developing a method for

collection of data

Complete/4

Formulates a focused problem/research question and identifies the relevant variables with a high degree of effectiveness.

Designs a method for the effective control of the variables with a high degree of effectiveness

Develops a method thatallows for the collectionof sufficient relevant data with a high degree of effectiveness

Mostly Complete/3

Formulates a focused problem/research question and identifies the relevant variables with considerable effectiveness

Designs a method for the effective control of the variables with considerable effectiveness

Develops a method thatallows for the collectionof sufficient relevant data with considerable effectiveness

Partial/2

Formulates a focused problem/research question and identifies the relevant variables with some effectiveness

Designs a method for the effective control of the variables with some effectiveness

Develops a method thatallows for the collectionof sufficient relevant data with some effectiveness

Not at all/1-0

Formulates a focused problem/research question and identifies the relevant variables with limited to no effectiveness

Designs a method for the effective control of the variables with limited to no effectiveness

Develops a method thatallows for the collectionof sufficient relevant data with limited to no effectiveness

Thinking and Investigatio

n/10

Data collection and processingLevels

Recording raw data

Processing raw data

Presenting processed data

Complete/4

Records appropriate qualitative and quantitative raw data, including units, with a high degree of effectiveness

Processes quantitative raw data with a high degree of effectiveness

Presents processed data with a high degree of effectiveness

Mostly Complete/3

Records appropriate qualitative and quantitative raw data, with considerable effectiveness

Processes quantitative raw data, with considerable effectiveness.

Presents processed data appropriately, with considerable effectiveness

Partial/2Records qualitative and quantitative raw data, with some effectiveness

Processes quantitative raw data with some effectiveness

Presents processed data with some effectiveness

Not at all/1-0Records qualitative and quantitative raw data, with limited to no effectiveness

Processes quantitative raw data with limited to no effectiveness

Presents processed data with limited to no effectiveness

Communication /10

Conclusion and Evaluation

Levels Conclusion

Evaluating procedure(s)

Improvements

Complete/4

States a conclusion, with justification, based on a reasonable interpretation of the data with a high degree of effectiveness

Evaluates weaknesses and limitations with a high degree of effectiveness

Suggests realistic improvements in respect of identified weaknesses and limitations with a high degree of effectiveness

Mostly Complete/3

States a conclusion based on a reasonable interpretation of the data with considerable effectiveness

Identifies weaknesses and limitations with considerable effectiveness

Suggests realistic improvements in respect of identified weaknesses and limitations with considerable effectiveness

Partial/2States a conclusion based on a reasonable interpretation of the data with some effectiveness

Identifies weaknesses and limitations with some effectiveness

Suggests realistic improvements in respect of identified weaknesses and limitations with some effectiveness

Not at all/1-0

States a conclusion based on a reasonable interpretation of the data with limited to no effectiveness

Identifies weaknesses and limitations with limited to no effectiveness

Suggests realistic improvements in respect of identified weaknesses and limitations with limited to no effectiveness

Thinking and

Investigation

/10