Vary an independent factor to see whether it affects the activity of the enzyme Catalase, using Hydrogen Peroxide (H2O2) and a potato solution (which has Catalase in it).

Research

• Definition of an enzyme: Enzymes are protiens that help speed up reactions (chemical). They are vital in life as life would not be able to go on, as reactions would not be fast enough. Enzymes are temperature sensitively and only like working at an optimum temperature. If this temperature goes over the optimum temperature, the enzyme denatures and becomes unusable. They are also sensitive to pH, as each enzyme prefers working in different pH environments.
• Definition of Catabolism: Catabolism is the break down of complex molecules into simpler forms. The reaction I am using is the break down of Hydrogen Peroxide into Water and Oxygen. The balanced equation for this is below:

2H2O2  => 2H2O + O2 

• The optimum temperature for Catalase is usually around 40 – 45°C. This is the temperature the enzyme works best at. However this can change in a potato as it depends where it is grown. In a hot country like Spain the optimum temperature for a potato maybe 45 – 50°C but in England where the atmosphere is a lot cooler, the optimum temperature might be around 35 - 40°C.

• As the temperature of the enzyme decrease below the optimum temperature, the more time it will take to produce the same amount of gas as an enzyme that is in an environment of its optimum temperature. But if the temperature, which the enzyme is in, is higher than the optimum temperature, the enzyme becomes de-natured and doesn’t act as a catalyst at all.

Prediction

   I predict that the optimum temperature for producing the same amount of gas in the shortest time will be around the 40 - 45°C. This is because the average optimum temperature of Catalase is around 40 - 45°C. Anything below that temperature will take longer to produce a certain amount of gas and any temperature above this will denature the enzyme, so it will have no affect on the result. I have worked this out using my research above and my general knowledge. I have carried out a preliminary experiment to test out a plan and get an idea where my range should be for the real investigation. I decide to time how long the temperatures 30, 40 and 50°C would take to produce 50ml of Oxygen, using a solution of 5g of potato with 15ml of water, and then reacted with 20ml of Hydrogen Peroxide. Here are my results:

The results show that 40°C is the shortest time to produce 50ml of gas. Using these results I can draw a preliminary graph of what the results should look like.

I have decided to use a range of 20, 25, 30, 35, 40, 45 and 50°C temperature for the investigation to get a good range of accurate results. I am going to see how long it takes to produce 50ml of Oxygen using 5g of Potato, 15ml of Water and 20ml of Hydrogen Peroxide.

Plan: -

Apparatus: -    Potato Solution: 35g of Potato and 105ml of Water

                20ml Hydrogen Peroxide

                Water baths at 20, 25, 30, 35, 40, 45 and 50°C

                Burette

                Burette Clamp

                Thermometer

                Stand

                Timer

                Conical Flask

                Delivery tube

                Food Processor

                Scalpels

                Scales (with tray)

                Measuring Cylinder

Method: -

   Set up the apparatus as shown. Weight out 35g of potato and put it in the food processor. Add 105ml of water to the potato and switch on the food processor until it has turned into a liquid solution. Measure out 20ml of this solution and put in a conical flask. Then put the conical flask in a water bath at 20°C and leave it until the temperature of the solution is 20°C, using the thermometer. Then measure 20ml of Hydrogen Peroxide in a measuring cylinder. Fill a burette with water and then tip it upside down without letting any water escaping. Place the open end in the water bath and hold in place using the burette clamp so the open end of the burette is in the water. Release any extra water, until it reads 50ml on the burette by opening the value slowly. Then get the delivery tube and place the tube end into the open end of the burette under the water (This creates an airtight seal where the oxygen produced cannot escape and has to go up the burette). Then add the 20ml of Hydrogen Peroxide to the potato solution, place the bung end of the delivery tube on the conical flask. Start the timer. As the gas is collected in the burette, the water level will decrease in the burette. When the water decreases to 0ml, stop the timer and record the time. Then repeat this for the other temperatures using the same potato solution and Hydrogen peroxide. After this, repeat the whole investigation again to get repeat results and any obvious anomalous results should be repeated again.

Fair Test: -

   To make it a fair test you must carry out these precautions: -

• The measuring of the Hydrogen Peroxide and Potato solution are accurate by using an ideal measuring cylinder.
• Don’t use the same measuring cylinder for the Hydrogen Peroxide and the Potato solution because it might contaminate the solutions and make it an un-accurate and un-fair test.
• Make sure that all apparatus are clean out properly after each result.
• Make sure the scales start on 0.00 grams
• The temperature of the potato solution is correct and does not change during an experiment.
• Make sure the pH of the potato solution does not change as well as it can affect the experiment. To stop this from happening make sure you use the same potato solution for each experiment.

Safety: -

   To make it a fair test you must carry out these precautions: -

• Wear Safety Goggles at all times.
• Bags and Stalls are put on the sides of the room, out of the way of any experiment.
• The normal Science Labs rules must be obeyed.
• Be careful with harmful substances.
• Watch out for Glass objects, which might get broken.

Results: -

* = Anomalous Result