Safety. Although the risks in the following experiments are minimal, you are advised to consult the latest edition of “security measures in school Laboratory ‘out of The Association for Science Education (ase.org.uk) before embarking on any attempt.
Outline. catalase is an enzyme that occurs in the cells of many species. Certain of the energy-releasing reactions in the cell produce hydrogen peroxide as a final product. This compound, which is toxic to the cell, is divided into water and oxygen by the action of catalase. 2H2O2 = 2H2O + O2
Samples of liver and yeast are dropped hydrogen peroxide. Oxygen is developed and the student is asked to extend the experiment to try to determine whether the enzyme in tissue responsible. The experiments and questions, taking about one hour
Prior knowledge The presence of inorganic catalysts ..; enzymes contaminated boiling; oxygen relights glowing splint
Advance preparation and materials -. in each group
20 volume hydrogen peroxide 50 cm3
liver, about 1 cm cubes
distilled water 20 cm3
dried yeast 1 g
clean sand about 1 g
charcoal grain, 1 g
equipment – for Group
test-tube rack and 4 test-tube
tongs or come to push the liver tube
4 labels or spirit label
mortar and pestle
study Here is a pretty important test of plant and animal tissues to see if
they contain catalase.
(a) Label three test-tube
(b) Pour about 20 mm (width) of hydrogen peroxide to each tube.
(c) Cut the liver in three pieces.
(d) In order tube 1. Add a small piece of the liver, and tube 2 add a pinch of dried yeast.
(e) Put glowing splint in tubes 1 and 2, bringing it close to the surface of the liquid or in the upper part of the foam.
1 Describe what you saw happening and the effect of the glowing splint.
2 How interpret these comments?
3 Is there any evidence of this experiment so far, to indicate whether the gas comes from hydrogen peroxide or from solid?
4 Is there any evidence at this stage that the enzyme involved in the production of gas in this reaction?
(f) The tube 3 seats a few grains of coal and observe the reaction.
5 Could coal be enzymes? Explain your answer.
6 provided (i) the gas in (f) is the same as before and (ii) for coal is almost pure carbon, the result is charcoal help you decide on? source gas in this and previous experiments
(g) Assume that the hypothesis is that it is the enzymes and yeast that breaks hydrogen peroxide to oxygen and water; design and implement a control experiment to test this hypothesis.
7 Record (i) test, (ii) the reasons that led you to implement it, (iii) to advance
results, and (iv) conclusions.
(h) to wash out the test-tube. Design and conduct an experiment to see if the expected enzyme plant and animal materials can reduce and still retain their properties. The experiment should include monitoring.
8 Briefly describe your method, results and conclusions.
9 Assuming that the liver and yeast which contains an enzyme that cleaves hydrogen peroxide, is there any evidence to show that it is the same enzyme? What would need to do to find this out for sure
Discussion -? Replies
1 effervescence to occur in each case, there is a greater power with yeast, but with the liver. Glowing splint should relight.
2 Oxygen is produced.
3 There is no evidence to indicate whether liquid or solid is supplying gas. If students believe that confidence is unlikely to emit gas they could be reminded of marble and hydrochloric acid it is producing solid carbon dioxide. It seems less likely, though yeast and liver would both give off oxygen when treated with hydrogen peroxide, but the hydrogen peroxide should be given oxygen when treated with a variety of materials.
4 So far, there is no evidence enzymes.
5 A gas will come off, but not fast enough to relight a glowing splint. Charcoal could not
be enzymes that (a) it is the element and (b) it has been produced by the very high temperatures that would destroy enzymes.
6 Charcoal, factor, was not able to give off oxygen. The gas will come from
7 (i) experiment include funds tissues and then put them in hydrogen peroxide.
(ii) If the enzyme is involved,
(iii) no gas will be produced.
8 Students should grind the sample with a little sand and distilled water, filter and test the filtrate with hydrogen peroxide. Oxygen will be developed with force proportional to the witness when the original material were tested.
student to fund half of each extract and show that it loses its effectiveness.
9 There appears to be no fundamental reason for yeast and liver should not be different enzyme catalytic decomposition of hydrogen peroxide. To be sure on this point, the enzyme would have to be isolated and their chemical composition determined.