How will you test the specificity of catalase in this experiment?

Try this class experiment to detect the presence of enzymes as they catalyse the decomposition of hydrogen peroxide

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Health, safety and technical notes
Teaching notes
Additional information
Science project
How do you test catalase activity?
What is catalase and how do we test for it?
How can you improve the accuracy of potato catalase experiment?
What happens in a catalase and hydrogen peroxide experiment?

Enzymes are biological catalysts which increase the speed of a chemical reaction. They are large protein molecules and are very specific to certain reactions. Hydrogen peroxide decomposes slowly in light to produce oxygen and water. The enzyme catalase can speed up (catalyse) this reaction.

In this practical, students investigate the presence of enzymes in liver, potato and celery by detecting the oxygen gas produced when hydrogen peroxide decomposes. The experiment should take no more than 20–30 minutes.

Equipment

Apparatus

Eye protection
Conical flasks, 100 cm3, x3
Measuring cylinder, 25 cm3
Bunsen burner
Wooden splint
A bucket or bin for disposal of waste materials

Chemicals

Hydrogen peroxide solution, ‘5 volume’
Small pieces of the following (see note 4):
- Liver
- Potato
- Celery

Health, safety and technical notes

Read our standard health and safety guidance.
Wear eye protection throughout. Students must be instructed NOT to taste or eat any of the foods used in the experiment.
Hydrogen peroxide solution, H2O2(aq) – see CLEAPSS Hazcard HC050 and CLEAPSS Recipe Book RB045. Hydrogen peroxide solution of ‘5 volume’ concentration is low hazard, but it will probably need to be prepared by dilution of a more concentrated solution which may be hazardous.
Only small samples of liver, potato and celery are required. These should be prepared for the lesson ready to be used by students. A disposal bin or bucket for used samples should be provided to avoid these being put down the sink.

Procedure

Measure 25 cm3 of hydrogen peroxide solution into each of three conical flasks.
At the same time, add a small piece of liver to the first flask, a small piece of potato to the second flask, and a small piece of celery to the third flask.
Hold a glowing splint in the neck of each flask.
Note the time taken before each glowing splint is relit by the evolved oxygen.
Dispose of all mixtures into the bucket or bin provided.

Teaching notes

Some vegetarian students may wish to opt out of handling liver samples, and this should be respected.

Before or after the experiment, the term enzyme will need to be introduced. The term may have been met previously in biological topics, but the notion that they act as catalysts and increase the rate of reactions may be new. Similarly their nature as large protein molecules whose catalytic activity can be very specific to certain chemical reactions may be unfamiliar. The name catalase for the enzyme present in all these foodstuffs can be introduced.

To show the similarity between enzymes and chemical catalysts, the teacher may wish to demonstrate (or ask the class to perform as part of the class experiment) the catalytic decomposition of hydrogen peroxide solution by manganese(IV) oxide (HARMFUL – see CLEAPSS Hazcard HC060).

If students have not performed the glowing splint test for oxygen for some time, they may need reminding of how to do so by a quick demonstration by the teacher.

Additional information

This is a resource from the Practical Chemistry project, developed by the Nuffield Foundation and the Royal Society of Chemistry. This collection of over 200 practical activities demonstrates a wide range of chemical concepts and processes. Each activity contains comprehensive information for teachers and technicians, including full technical notes and step-by-step procedures. Practical Chemistry activities accompany Practical Physics and Practical Biology.

Health and safety checked, 2016

Science project

How do living cells interact with the environment around them? All living things possess catalysts, or substances within them that speed up chemical reactions and processes. Enzymes are molecules that enable the chemical reactions that occur in all living things on earth. In this catalase and hydrogen peroxide experiment, we will discover how enzymes act as catalysts by causing chemical reactions to occur more quickly within living things. Using a potato and hydrogen peroxide, we can observe how enzymes like catalase work to perform decomposition, or the breaking down, of other substances. Catalase works to speed up the decomposition of hydrogen peroxide into oxygen and water. We will also test how this process is affected by changes in the temperature of the potato. Is the process faster or slower when compared to the control experiment conducted at room temperature?

What happens when a potato is combined with hydrogen peroxide?

1 Potato
Hydrogen peroxide
Small glass beaker or cup

Divide the potato into three roughly equal sections.
Keep one section raw and at room temperature.
Place another section in the freezer for at least 30 minutes.
Boil the last section for at least 5 minutes.
Chop and mash a small sample (about a tablespoon) of the room temperature potato and place into beaker or cup.
Pour enough hydrogen peroxide into the cup so that potato is submerged and observe.
Repeat steps 5 & 6 with the boiled and frozen potato sections.

Watch each of the potato/hydrogen peroxide mixtures and record what happens. The bubbling reaction you see is the metabolic process of decomposition, described earlier. This reaction is caused by catalase, an enzyme within the potato. You are observing catalase breaking hydrogen peroxide into oxygen and water. Which potato sample decomposed the most hydrogen peroxide? Which one reacted the least?

You should have noticed that the boiled potato produced little to no bubbles. This is because the heat degraded the catalase enzyme, making it incapable of processing the hydrogen peroxide. The frozen potato should have produced fewer bubbles than the room temperature sample because the cold temperature slowed the catalase enzyme’s ability to decompose the hydrogen peroxide. The room temperature potato produced the most bubbles because catalase works best at a room temperature.

Catalase acts as the catalyzing enzyme in the decomposition of hydrogen peroxide. Nearly all living things possess catalase, including us! This enzyme, like many others, aids in the decomposition of one substance into another. Catalase decomposes, or breaks down, hydrogen peroxide into water and oxygen.

Want to take a closer look? Go further in this experiment by looking at a very small sample of potato combined with hydrogen peroxide under a microscope!

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How do you test catalase activity?

Pour 1-2 ml of hydrogen peroxide solution into a test tube. Using a sterile wooden stick or a glass rod, take several colonies of the 18 to 24 hours test organism and immerse in the hydrogen peroxide solution. Observe for immediate bubbling.

What is catalase and how do we test for it?

Catalase is an enzyme that converts hydrogen peroxide to water and oxygen gas. The test is easy to perform; bacteria are simply mixed with H₂O₂. If bubbles appear (due to the production of oxygen gas) the bacteria are catalase positive. If no bubbles appear, the bacteria are catalase negative.

How can you improve the accuracy of potato catalase experiment?

In this case, when increasing the temperature, the more oxygen gas will be produced. Therefore the effect of temperature on potatoes will give more accurate results as to which temperature produces the most enzyme.

What happens in a catalase and hydrogen peroxide experiment?

When hydrogen peroxide comes in contact with the cut, it reacts with the catalase enzyme in the damaged cells to produce oxygen foam. When the catalase reaction is conducted in a test-tube, the oxygen gas bubbles. The height of the foam is an indication of the amount of catalase activity present.

How will you test the specificity of catalase in this experiment? Catalase enzyme Lab