Abstract
This experiment sought to investigate the effect of substrate on activity of enzyme catalase. It was hypothesized that catalase can only influence the breakdown of hydrogen peroxide. Three test tubes were selected and labeled tube 1, tube 2, and tube 3. Catalase and hydrogen peroxide were added to tube 1; water and hydrogen peroxide were added into tube 2; and catalase and sucrose were added into tube 3. Bubble measuring 20mm was formed in tube 1 while no bubble was seen in tube 2 and tube 3. A conclusion was made that enzyme catalase can only influence the rate of reaction of hydrogen peroxide but not of any other substrate. This confirmed the hypothesis.
Introduction
H2O 2 2H2O + O2 Many chemical reactions in living cells lead to formation of hydrogen peroxide as a by-product. Hydrogen peroxide is highly toxic and can kill cells if left to accumulate in them. Therefore, catalase is needed by cells to break down hydrogen peroxide. It is the fastest enzyme known (Roberts and King 50).
Properties of enzymes include; specificity, reversibility, ability to work efficiently at low concentrations, and the ability to be denatured at high temperatures. Specificity refers to the ability of enzymes to work on specific substrates. This property is comparable to key and lock mechanism (Mader 64). An enzyme is able to operate on specific substrate in the same way a key operates on a specific lock. However, some enzymes operate on several similar substrates while others that are highly specific operate on only one specific substrate. Catalase is an example of such enzymes since it breaks down hydrogen peroxide only.
Materials and methods
Materials
Wax Pencil
3 test tubes
Catalase buffered at pH 7
Catalase non-buffered
Hydrogen peroxide
Water
Sucrose Solution
Method
The experiment was conducted as follows. First, three test tubes were labeled and marked with a wax pencil at 1cm and 5cm levels. Tube 1 was filled with catalase buffered at PH level of 7 up to the first mark. Hydrogen peroxide was then added into the tube up to the second mark and the test tube swirled to mix the content. The tube was left for 20 seconds for bubble to form. After that, observations were made and the height of bubble measured and recorded.
Next, tube 2 was filled with water to the first mark. Hydrogen peroxide was then added up to the second mark and the tube swirled to mix the content. It was then left for 20 seconds before the height of bubble was taken and recorded.
Lastly, tube 3 was filled up to the first mark with catalase. Sucrose solution was then added up to the second mark and the tube was then swirled to mix its content. The tube was then left for 20 seconds before observations were made and height of bubble taken and recorded.
Results
The table below shows results obtained.
Discussion
Out of the three tubes used, only tube 1 produced bubble whose height was 20mm. Heights of bubble in tube 2 and 3 were both 0mm. In tube 1, both substrate (hydrogen peroxide) and enzyme (catalase) were present. In tube 2, the enzyme catalase was lacking while in tube 3, the correct substrate (hydrogen peroxide) was lacking. Instead, there was sucrose which is not the correct substrate for catalase.
In tube 1, since all conditions necessary for the breakdown of hydrogen peroxide were present, a reaction occurred. Hydrogen peroxide was broken down into water and oxygen. The oxygen formed the bubble that was observed.
In tube 2, no bubble was formed since no reaction occurred. Reaction did not occur because there was no enzyme to stimulate it. In tube 3, an enzyme and a substrate were present. However, the substrate present (sucrose) is not the right one for catalase. This tube serves as negative control in the experiment. If bubbles would have been formed in tubes 2 and 3, it would have not been due to presence of catalase. Consequently, the experiment would have been regarded as invalid.
Conclusion
This experiment shows that enzymes are substrate specific: they influence rates of reactions that contain their substrates only. This is confirmed in the experiment by the fact that bubble was formed in tube 1 only since it had the right substrate. Other tubes did not show any bubble.
Works cited
Mader, Sylvia S. Biology. New York: McGraw-Hill Higher Education, 2010. Print.
Roberts, M B. V, and T J. King. Biology: A Functional Approach. Students' Manual. Walton-on-Thames, Surrey: Nelson, 1987. Print.
Toole, Glenn, and Susan Toole. Advanced Human and Social Biology. Cheltenham: Stanley Thornes, 1997. Print.
