Reasons for doing a pre-test
I am going to perform a pre-test so that I have an idea of the quantities of Hydrogen Peroxide and catalase I will need to use in my actual experiment. Doing a pre-test means I will get a more accurate result when it comes to the proper experiment.
Pre-test method
Apparatus
- Glass Beaker
- Measuring Cylinder
- Cork borer (I used number size. 3)
- Test tube
- Plastic bowl
- A separating tube
- Gather equipment and set up as shown below:
- Using the cork borer cut the potato into 3cm³
- Fill the Glass beaker with 20cm³of water set to the temperature chosen (For my pre-test I chose the temperatures 20°, 40° and 60°)
- Fill plastic bowl with tap water, place the measuring cylinder into the water itself filled with water and place one end of the separating tube into the measuring cylinder
- Put 5cm³of Hydrogen Peroxide in the test tube and place it in the glass beaker filled with preheated water
- Add the already cut piece of potato in the Hydrogen Peroxide
- Start timing for 2 minutes
- After 2 minutes measure how much gas was collected in the measuring cylinder
- Record these measurements into a results table
- Plot a graph and than evaluate it
Pre-test Results
Pre-test ConclusioN
My pre-test worked very well and the amounts of Hydrogen Peroxide and the length of time I chose worked so well I have decided to use them in my actual experiment. The only thing I will change in my experiment is that I will heat the Hydrogen Peroxide to the chosen temp before putting the catalase source in
Pre-test Evaluation
I used 60° for one of my temperatures and instead of the enzyme denaturing (like the scientific terms show it should) at 60° was when the most gas was collected. Enzymes are supposed to denature after 45°. This was because I didn’t let the Hydrogen Peroxide rise to the temperature of the water before dropping the potato
Prediction
For my actual experiment I predict that the more I raise the temp the more gas will be collected because enzyme activity is increased when the temperature increases. Raising the temperature will increase the random movements of the molecules and increase the chance of the substrate (Hydrogen Peroxide) and enzyme colliding. I must remember that although increasing the temperature increases enzyme activity a great increase of temperature, which cause the enzyme to denature. The special shape of the enzyme changes and the substrate will no longer fit in the active site. In other words the key will not fit the lock.
This is why this process is called the lock and key hypothesis.
The highest temperature an enzyme works at is 45°anything higher it will be denatured.
Method
I will gather and set up the experiment just as I did in the pre-test the only thing I will change now is the amount of times I will repeat the temperatures and the temperatures themselves, and also learning form my past mistake I will allow the Hydrogen Peroxide rise to the correct the temperature before dropping the potato in.
- After setting up the apparatus as before allow the Hydrogen Peroxide to heat up about 30 seconds and then drop the 3cm³ catalase in
- Using the same amounts of Hydrogen Peroxide as I did in my pre-test
- Record results after the two minutes are up
- Repeat for all temperatures and repeat every temperature 2 times
- Plot a graph
Results
Conclusion
My prediction was correct. When I increased the temperature the amount of gas collected did in fact rise proving sciences explanation. For example at 20°C the amount of gas collected was 0.15 and as the temperature raised to 40°C the amount of gas collected had risen to 1.6. Then as I said in my prediction that after 45°C the enzyme became denatured and the amount of gas collected decreased to 0.6 at 60°C. The of gas rose because the heat activated more energy in the enzyme which was breaking down the hydrogen peroxide to a gas so as the enzymes gained more energy the more they moved so the more they moved at collided with the hydrogen peroxide molecules (which the reaction to take place). Then at 50°C the results started to fall proving that the enzyme became destroyed by so much heat and couldn’t react as much, because their shape had been disfigured.
Evaluation
My experiment went to plan and the amounts of substances and the temperature ranges that I chose to use worked extremely well. There were no anomalous results on my graph. If I were to improve my experiment I would grate the potato into hydrogen peroxide instead of using a solid piece of potato this is because using a solid piece means that the catalase in the middle of the chunk is not being used because the hydrogen peroxide is only on the outside. The reaction will only take place on the surface but grating it using a pestle would mean using all of the catalase in the potato and a much speedier investigation.
