Variables
In my investigation I intend to vary the temperature of the liver that is reacting with the hydrogen peroxide.
I shall measure the temperature using a thermometer, to vary the temperature of the liver the test tube will be in a water bath.
Prediction
I think the strongest reaction with be at 40ºC.
Scientific Knowledge
I think the reaction will be like this because an enzyme works best at the body temperature and as body temperature is just below 40º, at a higher temperature the enzyme will be denatured and at a lower temperature the enzyme slows down.
The enzymes in the body do not work at the optimum temperature because they need to be a controlled reaction. Enzymes have an optimum environment for working this includes pH and temperature.
Fair Test
The things that I shall keep the same through my investigation are the amount of hydrogen peroxide and liver used, also the time that the reaction is measured for and the pH of the reaction.
Apparatus
- Liver
- Hydrogen peroxide
- Test tube
- Beaker
- Delivery tube
- Measuring cylinder
- Thermometer
- Stopwatch
- Reservoir of water
Diagram
Preliminary Work
The preliminary work I did was to find the best amounts of hydrogen peroxide and liver. The reaction was too vigorous with 5cm² and not strong enough with 2.5cm² of hydrogen peroxide. Also using a small piece of liver instead of a paste was easier, the paste was made by grinding the liver with sand and water.
Plan
First I shall set up my experiment and then measure the reaction using a stopwatch and a measuring cylinder for the following temperatures: 20º
30º
40º
50º
60º
In order to keep my results reliable I shall keep the same amounts of liver and hydrogen peroxide.
To ensure safety for myself and others I shall make sure that equipment is used properly and that ice and boiling water is kept in a safe place where it cannot injure anyone.
Results
Conclusion
The results show that the reaction is slowest at the lowest temperature, which agrees with the theory that enzymes work slowly at lower temperatures. The most violent reaction was at 40º, which also agrees with my prediction that the most violent reaction would be at the temperature closest to body temperature. After the optimum temperature the reactions then slows down again very quickly thus showing that enzymes only work efficiently at there optimum conditions.
Evaluation
To improve the investigation more accurate apparatus should be used. This would ensure that all the constants were kept precisely constant; this would mean that other factors wouldn’t effect the reaction. More accurate apparatus would also measure the reaction a lot more precisely and wouldn’t have to allow for the human reaction time such as with pouring the hydrogen peroxide, starting and stopping the stop watch and reaction.
Human errors can’t greatly affect the accuracy of results; reaction times vary from day to day and so are not very accurate, a computer taking the results in would be better as they are more accurate
The same liver should be used and the reactions done on the same day so the liver is at the same condition for the investigation as over time the enzymes may have become less effective.
