The Effect of Different Concentration of Hydrogen Peroxide on the Rate of Reaction of Catalase Enzyme.

                catalase

2H2O2                                2H2O + O2 

The aim of my experiment:

In this experiment I will investigate the effect of different concentrations of hydrogen peroxide on the rate of reaction of enzyme catalase extracted from potato.     

Equipments used in this experiment:

* Tools:

* 4 test tubes

* Evaporating dish

* Spatula

* Mortar and pestle

* Pipette

* Scalpel

* Forceps

* Balance

* Syringe

* Digital stopclock

* Materials:

*potato

* Solutions:

* Hydrogen peroxide solution    (H2O2)

* Water                                       (H2O)

Variables

The independent variable which are altered by me is the different concentration of Hydrogen Peroxide which are (0.5 mol, 1.0 mol, 1.5 mol, and 2.0 mol).

As for the dependant variables which is the rate of reaction it will be assessed by the time needed for a filter paper to stay in the bottom of the test tube before start to rise up in the hydrogen peroxide solution.

Other variables that affect the rate of catalase reaction will be controlled such as:

• The temperature will be kept at room temperature 20°C
• The volume of water in the Syringe will be 15 ml
• The filter paper will be cut into equal piece of 1cm2
• The amount of hydrogen peroxide in the test tube will fixed for all test tubes by marking 4 cm with the marker on the test tubes and filling them with hydrogen peroxide till the mark
• The weight of the potato will be 17.3 gm.

These variables will be controlled to achieve a fair test.

Procedure

Preliminary work

Before starting the experiment a pilot test was conducted to get acquainted with the steps of the experiment and especially when measuring the results, practicing the precautions and controlling the variables.

In order to prepare the concentration of hydrogen peroxide, I will use the following table to get the concentration of hydrogen peroxide before making my experiment.  

1. At first I will cut a piece of a potato using a scalpel  and weight it on a balance to know its weight.
2. I will use a mortar and pestle to grind the potato. I will add water to the grind potato using a syringe, also I will add some sand.
3. The potato will break down with the help of water and sand to extract the catalase enzyme from it.
4. I'm going to dip small equal sized filter paper using a forceps into the catalase enzyme solution which is formed from grinding the potato.
5. The filter paper will absorb the catalase enzyme solution so as to be used easily in the test tubes.
6. I will  prepare four test tubes, mark 4 cm with the marker on each test tube and fill each with a different concentrations of hydrogen peroxide (0.5 mol, 1.0 mol, 1.5 mol, and 2.0 mol) using a pipette.
7. I will dip a piece of filter paper in each test tube.
8. Using a digital stopclock,  I will record  the time from when the filter paper reaches the bottom of the test tube till it starts to rise up again, this will be repeated for each test tube.
9. I'm going to repeat the experiment three times for each test tube (to make sure the results are reliable), take three readings and take the average time for each test tube; this will be my records that I'm going to work on.

Precautions

While doing the experiment we have to be careful in:

1. Using some tools or to be aware avoiding the solutions which may be harmful to sensitive parts such as the mouth or the eyes.
2. Using the scalpel.
3. Wearing gloves to avoid the contact with harmful substance.
4. Washing the test tubes well with water and dry it in order not to affect the solution that will be used in it.
5. Cutting the filter paper into equal pieces not to affect the rate of the enzyme.
6. Using the stopclock accurately, and in watching the filter paper while touching the bottom and start rising up.    

All these precautions must be done so as to obtain accurate results.

Prediction:

I predict that the effect of changing Hydrogen Peroxide will be that as the concentration of hydrogen peroxide increases the time needed for the filter paper to stay in the bottom of the test tubes before starting to rise up the test tube (which is the time of the catalase reaction on hydrogen peroxide) decreases  and vise versa.

The reason for this results is that the  rate of an enzyme action increases as the concentration increases because more of the active sites of the enzyme are being used which results in more reactions (quicker) so the time needed for the reaction to be finished decreases.  

OBTAINING EVIDENCE

Results

I carried out the above procedures and was very careful while using the equipments and materials in order not to harm myself and students working around me so I was careful in:

• Using some tools and avoiding the solutions which may be harmful to sensitive parts such as the mouth or the eyes (hydrogen peroxide).
• Using the scalpel.
• Wearing gloves to avoid the contact with harmful substance.

And  in order to avoid the errors and achieve a fair test for each experiment I carried out :

• I made the experiments at room temperature 20°C.
• I used water in the Syringe with volume 15 ml.
• I cut the filter paper into equal piece of 1cm2.
• I fixed the amount of hydrogen peroxide in the test tube at 4 cm.
• I made the weight of the potato 17.3 gm.

Carrying out the experiment 3 times for each concentration of Hydrogen Peroxide (0.5 mol, 1.0 mol, 1.5 mol, and 2.0 mol). I recorded the following results:

1st experiment result table (concentration/time) :

2nd  experiment result table (concentration/time):

3rd  experiment result table (concentration/time):

Then I calculated the average time from the 3 previous experiments as follows (concentration/time):

ANALYZING EVIDENCE

From the above results I plotted the following graphs for each of the 3 experiments:

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Then I plotted the following graph for the average time calculated from the 3 experiments.

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Then I plotted the following graph including line of best fit for the average time calculated from the 3 experiments.

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Trend and Pattern

We could notice from the graphs that the curve decreases, which means that reaction time is inversely proportional to the concentration H2O2. First at concentration 0.5 mol the average reaction time was 14 seconds, then increasing the concentration to 1.0 mol the reaction time falls rapidly to 7 seconds and so on till it reaches 3 seconds at 2 mol concentration of H2O2. Also, the graph shows that the decrease in reaction time (slope of the curve) is higher when the concentration is increased from 0.5 mol to 1.0 mol, compared to slight decrease in reaction time with further increase in concentration.    

This indicates that as the concentration of Hydrogen Peroxide increases the time needed for the filter paper to stay at the bottom (finish reaction) of the tube decreases. Thus as the concentration of hydrogen peroxide increases the rate of an enzyme action increases. The reason for this is that as the concentration of hydrogen peroxide increases more of the active sites of the enzyme are being used by hydrogen peroxide and thus the reaction happens faster.

These results support my earlier prediction while planning for my work.

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Evaluating:

The method that I have applied gave good results that are consistent with my prediction. The graphs that I plotted had clearly showed the effect of the different concentrations of hydrogen peroxide on the rate of reaction of enzyme catalase extracted from potato.

The reason that my results are accurate and reliable is that I managed to achieve a fair test through the following:

• using the same equipment and tools
• using the same potato with a fixed weight of 17.3 gm
• carrying out my experiments at same room temperature at 20°C

• using equal size of filter paper of 1cm2.

Moreover, I carried out the experiment 3 times for each concentration of Hydrogen Peroxide (2.0 mol, 1.5 mol, 1.0 mol, and 0.5 mol) and I calculated the average of the 3 experiments for each concentration.

From my results and graphs I think that I have enough evidence to draw a firm conclusion that there is a relational between the concentration of  hydrogen peroxide and the rate of reaction of enzyme catalase. This means that increasing the concentration will decrease the reaction time and this is illustrated in the graphs.

So as to improve my method to obtain more evidence to support my conclusion, I suggest to increase the concentration of hydrogen peroxide more than 2 mol and observe the results. On the other hand, I also believe that increasing the concentration gradually will reach a point above which there will be no further decrease in reaction time and the reaction rate will become stable.    

I will also try to apply the same experiment on other types of plant cells other that potato to observe the results such as carrot or beetroot and also apply on animal cells to compare between the different results.