Safety. from
Although the hazards in the following experiments are negligible, it is recommended that you review the latest edition of the "School Laboratory Safeguards" published by the Science Education Association [ase.org.uk] before starting any experiments.
Outline. from
Catalase is an enzyme found in many living organisms. Certain energy release reactions in the cells produce hydrogen peroxide as the end product. This toxic compound is split into water and oxygen by the action of catalase. 2H2O2 = 2H2O + O2
The liver and yeast samples were dropped into hydrogen peroxide. As oxygen evolved, students were asked to extend the experiment to try to determine if the enzymes in the tissue were responsible. Experiments and questions take about an hour.
Prior knowledge. from
The presence of an inorganic catalyst; enzymatic boiling denaturation; oxygen makes people glow.
Advance preparation and materials - each group
20 volumes of hydrogen peroxide 50 cm3
Splint
Liver, about 1 cm cube
Distilled water 20 cm3
Dry yeast about 1 gram
Clean sand about 1 gram
Activated carbon granules, about 1 gram
Instruments - each group
Test tube rack and 4 test tubes
Tweezers or seekers for pushing the liver into a test tube
4 labels or spirit tags
Filter funnel
Bunsen burner
Filter paper
Test tube holder
Research and development
experiment
The following survey is a fairly rigorous examination of plant and animal tissue to see if
They contain catalase.
[a] Mark three tubes 1-3.
[b] Pour about 20 mm [depth] of hydrogen peroxide into each tube.
[c] Cut the liver into 3 pieces.
[d] Add a small piece of liver to tube 1 and add a little dry yeast to tube 2.
[e] Insert the illuminating splint into the tubes 1 and 2 so as to be close to the liquid surface or the upper portion of the foam.
1 Describe what you see and how it affects the illuminated splint.
2 How do you understand these observations?
3 So far, is there any evidence in the experiment that the gas is from hydrogen peroxide or from solids?
4 At this stage, is there any evidence that the enzyme produces gas in this reaction?
[f] A few pieces of charcoal particles were placed in the tube 3 and the reaction was observed.
5 Can charcoal be an enzyme? Explain your answer.
6 Suppose the gas in [i][f] is the same as before, and [ii] the charcoal is almost pure carbon. Does the charcoal result help you determine the source of the gas in this gas and previous experiments?
[g] Hypothesis hypothesis that there is an enzyme in the liver and yeast that decomposes hydrogen peroxide into oxygen and water; a control experiment was designed and tested to test this hypothesis.
7 records [i] the experiment, [ii] the cause of your experiment, [iii] observed
Results and [iv] your conclusions.
[h] Rinse the tube. Experiments were conducted and experiments were performed to determine whether so-called enzymes in plant and animal materials could be extracted and still retain their properties. The experiment should include a control.
8 Briefly describe your procedures, results and conclusions.
9 It is assumed that both the liver and the yeast contain an enzyme that decomposes hydrogen peroxide. Is there any evidence that it is the same enzyme? What must be done to determine?
Discussion - the answer
1 Effervescence should be observed in each case, but yeast is more active than the liver. The illuminated splint should be lit again.
2 is producing oxygen.
3 There is no evidence of whether a liquid or solid will produce a gas. If students believe that solids are less likely to release gas, they may be reminded of marble and hydrochloric acid, where solids produce carbon dioxide. However, it seems unlikely that both yeast and liver will release oxygen when treated with hydrogen peroxide, while hydrogen peroxide should provide oxygen when treated with various materials.
So far, there is no evidence of the presence of enzymes.
5 The gas will fall off, but it will not reignite the illuminated splint quickly enough. Charcoal can't
It is an enzyme because [a] it is an element, and [b] it is produced by very high temperatures, which destroys the enzyme.
6 Charcoal is an element that does not release oxygen. Gas must come from
hydrogen peroxide.
7[i] The experiment should include boiling the tissue and then placing them in hydrogen peroxide.
[ii] if an enzyme is involved,
[iii] No gas is produced.
8 Students used a small amount of sand and distilled water to grind the sample, filtered and tested the filtrate with hydrogen peroxide. Oxygen will evolve in a manner that is proportional to the vitality seen when testing the original material.
Students should boil half of each extract and indicate that it has lost activity.
9 There seems to be no root cause. Yeast and liver should not have different enzymes to catalyze the decomposition of hydrogen peroxide. To determine this, the enzyme must be extracted and its chemical composition determined.
Orignal From: Teacher's Biological Experiment - Enzyme: Catalase
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