Investigating the Effect of Hydrogen Peroxide on Liver Catalase

An enzyme is a biological catalyst produced in cells that is capable
of speeding up the chemical reactions necessary for life. Enzymes are
large complex proteins, which are very specific. Each chemical
reaction in the body requires it's own particular enzyme. Each enzyme
is specific because of the shape it forms in order to react with the
right part of a molecule. After a reaction has taken place the enzyme
falls away from the molecule. The enzyme is unaltered. The process
then repeats itself. One such enzyme is catalase.

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Variables

There are several variables that will all affect the reaction between
Hydrogen peroxide and liver catalase. These are:

Ø The Temperature

Ø The dilution of the Hydrogen peroxide

Ø The amount of catalase

Ø The PH of the surrounding environment

The variable that I have chosen to investigate is temperature.

Prediction

It is my belief that the hydrogen peroxide will react best with the
liver catalase at around 37°C.

Hypothesis

I have predicted this because the liver catalase will be used to
working best at body temperature. Natural body temperature is usually
37°C This means that at this temperature the liver catalase will have
a stronger reaction with the hydrogen peroxide. Above this temperature
the enzymes may denature and will not work efficiently, if at all.

Catalase is an enzyme that is found in the liver. It is found
extensively in mammalian tissues. It is present in the body to prevent
the excess build up of hydrogen peroxide in the body. Hydrogen
peroxide is created continuously by numerous metabolic reactions. In
large quantities peroxide can be harmful to bodily tissues and so
needs to be kept to an adequate level.

Apparatus

Bunsen Burner, 10x test tubes, tripod, gauze, heat-proof mat, beaker,
water, stirring rod, thermometer, timer, 300cm3 of Hydrogen peroxide,
measuring cylinder and 30 pieces of liver (each 1cm3).

Diagram


[IMAGE]
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Method

1 The apparatus was set up as shown in the diagram.

2 The first test was prepared at the right temperature (20°C) and the
first piece of liver was placed into the test tube.

3 The stirring rod will be used to hold the liver in the test tube as
the reaction is timed.

4When the reaction has stopped the time displayed on the timer will be
recorded into a results table.

5 The next test tube of Hydrogen peroxide will be heated to the
desired temperature between 20°C and 90°C and steps 2 - 4 will be
repeated.

6 This whole process (steps 2 - 5) will be repeated three times in
order to obtain a more accurate set of results.

Fair Test

Ø Only the temperature of the Hydrogen peroxide will change throughout
the investigation.

Ø The amount of Hydrogen peroxide in each test tube will be the same.

Ø The amount of liver placed into the test tubes will be the same size
(1cm3).

Safety

During the investigation whilst heating the Hydrogen peroxide the
whole group will be standing up and wearing safety glasses.


Results
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Reaction 1

Reaction 2

Target

Accurate

Time

Target

Accurate

Time

Temp.

Temp.

Taken

Temp.

Temp.

Taken

(Celsius)

(Celsius)

(sec)

(Celsius)

(Celsius)

(sec)

20

22

218

20

23

100

30

32

38

30

30

26

40

41

44

40

40

22

50

50

33

50

52

22

60

60

29

60

60

20

70

73

61

70

71

50

80

83

31

80

79

13

Analysis

Having drawn a graph and considered my results I can see that the
Hydrogen peroxide appears to form a straight-line pattern. This shows
that as the temperature rises, the rate of reaction rises as well.
However, most of my results follow this pattern but there are several
that appear to be anomalous. The first set of results I gathered are
completely different to the second set of results I gathered but the
general trend is that the time eventually decreases, by quite a
margin, as the temperature increases. Perhaps my prediction was wrong
and the enzyme, catalase, increases its efficiency as the temperature
increases and does not work best at 37°C This may suggest an unstable
solution was used. I know that hydrogen peroxide denatures very
quickly. The reaction time appears to decrease as the temperature
rises. This is visible in both of the sets of results that I have
gathered.

Conclusion

I was expecting the catalase to react best with the hydrogen peroxide
at around 37°C but this does not seem to be the case. The reaction
times seem to be linear. The reaction time decreases accordingly with
the increase in temperature. If this is true then my prediction was
wrong. I have reason to believe however that most of my results are
anomalous.

Evaluation

It is my opinion that the investigation that I have carried out into
the affect of liver catalase with hydrogen peroxide was in fact not a
success. I believe that the results I have gathered maybe completely
anomalous. This could be due to the rapid denaturing of the hydrogen
peroxide in the air or through inaccurate timing and observations.

To prevent inaccurate results if I were to carry out the investigation
again I would use a more accurate timing method such as a digital
timer. An analogue watch is not accurate enough method of timing to
gather effective results. I would also consider when the reaction
starts and finishes and then stick to that assumption. During the
investigation the observations I carried out were not accurate. I can
tell this by looking at my graph; the results do not run smoothly,
there are two results that are a long way from the line of best fit
that suggests that these two results have to be anomalous. It was
difficult to tell exactly when a reaction had stopped as bubbles were
constantly being produced by the hydrogen peroxides denaturing.