In this investigation I will be able to watch the action of catalase in a test tube and compare it with an inorganic catalyst that causes the same reaction.
Variables
To ensure this experiment is completed as fairly as possible, all the variables except for the concentration of Hydrogen Peroxide must be kept the same for all experiments; this is the independent variable. Variables that must not be altered include, dependent are:
Temperature, Catalase Concentration, and pH.
When measuring the volumes of water and Hydrogen Peroxide, the measurement should be taken from a 90-degree angle to avoid parallax error.
Measurements
I shall be using the following concentrations:
- 0M = 50ml of distilled water
- 0.2M = 40ml of distilled water and 10ml of hydrogen peroxide
- 0.4M = 30ml of distilled water and 20ml of hydrogen peroxide
- 0.6M = 20ml of distilled water and 30ml of hydrogen peroxide
- 0.8M = 10ml of distilled water and 40ml of hydrogen peroxide
- 1M = 50ml of hydrogen peroxide
Equipment
- Test tubes x6
- Corks with delivery tubes x6
- Petri dish
- Measuring cylinders x6
- Thermometer
- Hydrogen peroxide
- Potato
- Test tube rack
- Scalpel
- Water bath
- Distilled water
- Stop clock
Method
- Firstly I will be cutting my potato in half and then cutting 6 cubes of 1cm² with my scalpel on a cutting tile. I shall leave these pieces on a petri dish in distilled water to stop the pieces becoming dry.
- Then I will take my first test tube which will be prepared with 0M (50ml distilled water). I will then leave this test in a water bath at 20°C so that the content of the test tube is at the right temperature. I have chosen 20°C because this is the temperature where the enzyme catalase is at its optimum. At this temperature the enzyme and the substrate are reacting the quickest they can. As the piece of potato is put into the tube I shall straight away put a cork on top which will have a delivery tube coming out of the test tube which is connected to a syringe, the syringe is used to collect the oxygen produced from the reaction.
- I shall be leaving the reaction to occur for 90 seconds and I shall then disconnect the delivery tube from the test tube and then seal the ends, letting the remaining oxygen enter the syringe. I shall mark the level of oxygen collected and then note this down in a table.
- I will be repeating this method with each concentration and then repeat each concentration 5 times to get a good average. When I set up my syringes I will make sure that there are no air bubbles present so that my results are not affected. To keep the temperatures constant I will be using a water bath; this is so that the enzyme is always working at its optimum temperature. Finally too keep the pH at pH7 I shall be using a buffer solution, a buffer solution keeps a pH constant.
Preliminary work
For my preliminary work I carried out an experiment investigating how the enzyme catalase reacted with various different specimens. The specimens I used were liver, kidney, potato and apple. The largest reactions were with the liver and the potato. There was lots of fizzing and foaming with the hydrogen peroxide, which shows that gas was being given off. Doing this preliminary work was good preparation, for when it comes to do final experiment, this is because I will now be more organised and quicker at getting the equipment ready for the experiment.
Prediction
I predict that as the substrate concentration increases, the rate of reaction will go up at a directionally proportional rate until the solution becomes saturated with the substrate Hydrogen Peroxide. When this saturation point is reached, then adding extra substrate will make no difference. The rate steadily increases when more substrate is added because more of the active sites of the enzyme are being used which results in more reactions so the amount of Oxygen released in a given time is higher. Once the amount of substrate molecules added exceeds the number of active sites available then the rate of reaction will no longer go up. This is due to the maximum number of reactions being done at once, so any extra substrate molecules have to wait until some of the active sites become available.
Table of Results