This showed me that this range is too low because there is no optimum rate of reaction so I chose to change the range to 20oC to 60oC at 10oC intervals so, as I would get an Optimum rate. I chose this rate based on that the human body is approximately 37oC.
The preliminary work solved these issues:
Research: Catalase is an enzyme found in all living cells. It makes Hydrogen Peroxide decompose into water and oxygen.
The reaction in the experiment is affected by the following Variables:
-
Thickness- if the potato is made thicker the surface Area will be greater so the reaction will be quicker. This will also affect the amount of Catalase which is the potato because if the potato is thicker there will be more Catalase.
-
Concentration- if concentration is increased the rate of enzyme action is increased because there will be more Catalase in the same area so the reaction will be greater. This also applies for the Hydrogen Peroxide because if there is more Hydrogen Peroxide in a certain area there will be greater chance for the enzyme to react.
-
Temperature- this will speed up the movement of the enzyme Catalase because they have more energy therefore increasing the rate of enzyme action. It will also increase the rate of the movement of the Hydrogen Peroxide because they will have more energy. This will increase the chance of the Enzyme molecules and Hydrogen Peroxide molecules meeting and there for the rate of reaction will increase. If the temperature gets too high the enzyme becomes denature, this is when the active site of the enzyme is changed so it cannot do it’s specific function.
-
Type of potato- the Permeability and Turgidity may differ from one type to another. This may affect the amount of Hydrogen Peroxide the potato can hold to react and also how much it will absorb.
-
Volume- If there is a greater volume of Catalase or Hydrogen Peroxide in one of the reactions than an other there will more enzymes working quickening the reaction or in the case of the hydrogen peroxide here will be a greater chance of the enzyme and the Hydrogen Peroxide meeting if there is a greater volume in one reaction.
-
pH- this affects the active site of the enzyme, it can denature the Enzyme by changing the shape of the active site so it can not do it’s specific site.
Controlling Constants:
Potato size: The dimensions of the potato will be kept constant by always using an 8mm Cork Borer and always making the segments 2cm long this will cover all the dimensions o the potato.
Concentration: This will be kept constant by always using the same concentration of liquids provided.
pH: The pH will be kept constant by not changing the pH of the Hydrogen Peroxide and the Enzyme, Catalase.
Volume of hydrogen Peroxide: This will be kept constant at 25ml by using a measuring cylinder.
Apparatus: This will be kept constant by using my preliminary work r chose appropriate apparatus that will give me accurate results and using the same apparatus.
Starting of Stopwatch: I have chosen to regulate the starting point of the stopwatch this will always be started at when the rubber bung with the delivery tube in it has been inserted.
Apparatus and Chemicals used in experiment:
1x 25ml Measuring Cylinder
Hydrogen Peroxide
Water
Potato
8x Test Tubes
1x Delivery Tube with bung
Test Tube Rack
4x Water Baths (one at each of the following temperature 300C, 400C, 500C, 600C.)
2x thermometer
2x Cork Borers (one 8mm and the other of smaller dimension)
1x Stopwatch
1x Cutting Tile
1x Scalpel
1x Ruler
Picture of Apparatus:
Method:
- I collected the apparatus, which is listed above I then, set it up as pictured above.
- I then measured 25ml of the Hydrogen Peroxide using a measuring cylinder. I put this into a test tube.
- I then, using the 8mm cork borer cut a segment of potato. I then used a cork borer of smaller dimensions to remove the segment of potato. I cut, using the scalpel and cutting tile, the skin off of this potato and made sure it was 2cm long with a ruler.
- I then put this segment of potato into another test tube.
- I then put the test tube with the hydrogen peroxide and test tube with the potato into the water bath with the appropriate temperature.
- I then put a thermometer into each of the test tubes in the water baths.
- Once the thermometer showed the appropriate temperature I took the test tubes from the water baths. I removed the thermometers and put both the potato and the hydrogen peroxide into the test being held in the clamp stand (shown above).
- Once both the test tubes are empty I put the orange bung with the delivery tube onto the top and started the stopwatch.
- I then timed for a minute, counting the bubbles in a tally form.
- I then repeated the procedure from steps 2 to 9 for all the temperatures.
- I repeated every temperature 3 times.
Safety Aspects:
The reaction above shows that there are no harmful products so the experiment is safe.
There are many other safety factors which have to be regulated.
Experiment Appartus should only be used for safety.
Saftey Goggles must be warn to protect eyes from accidents with Hydrogen Peroxide, which can irrate eyes and can also cause chemical burns to skin. Care should be taken when handling hydrogen Peroxide the the Enzyme Catalase, Plastic Gloves are adviceable.
Results obtained form experiment:
I am also going to find the rate of a reaction by using the following formula. I used this to more specific results, as I always used 60 seconds as my time taken, I will use the following formula:
I therefore found the results below:
Analysis of results
From the results I have collected I have enough evidence to say that when the enzyme, Catalase is heated it’s rate of reaction increases until it reaches an optimum point. My hypothesis was that the number of bubbles counted in a minute would increase, this was proven correct by my results. Also I predicted an optimum temperature of around 40 oC but this was wrong because the optimum was approximately 50oC. There is a rough correlation that every 10 oC increase the number of bubbles goes up by 10 this is true until it reaches 50 oC when it drops dramatically.
All my graphs came up with the same curve feature, showing that there is an optimum temperature for the enzyme to work this optimum temperature is shown to be around 50oC. This is slightly higher than expected but this must mean that the enzyme Catalase is not working at its optimum rate in the human body, but it may work at a faster rate of reaction in a warmer bodied animal. After the optimum point of 50oC, the number of bubbles and therefore the rate of the reaction decrease very quickly to around 3 bubbles counted a minute, this s due to enzyme being denatured. This denaturing is based on the Lock and Key Theory that enzymes are specific and one enzyme can only catalyse one substrate and when a temperature gets too high the enzyme’s protein structure is altered. The active site of the enzyme changes shape and the substrate does not fit into the active site to be broken down so little or no reaction happens.
The particle theory is the bases of this experiment and all predictions were made from it so this investigation agrees with the particle theory.
Evaluation
The experiment went as according to plan and we collected accurate results because we followed the method and also our safety aspects. We also used appropriate apparatus safely and accurately this made me collect accurate results. There were not spillages in the investigation so no contamination happened to the potato and the hydrogen peroxide, this increased the accuracy of the results. I collected no anomalies in this experiment but this was due to the use of an accurate method and the processing of my results into rates of reactions and averages.
This investigation could however be improved by taking a larger range of temperature at more frequent intervals this would give you also a more accurate optimum temperature and greater understanding of the process of Enzyme Action. I could not do this due to lack of time and resources. I may have collected data that could be inaccurate because when the potato and the Hydrogen peroxide are mixed, I had to push the bung and delivery tube into the top of the test tube and I had to start the stopwatch add and also count bubbles. I could have missed a bubble and also I could have started the stopwatch too late or too early and when the bung is pushed in this causes the air inside the test tube to be compressed. Therefore bubbles of air not oxygen can be produced and can be mistakenly counted as oxygen produced by the reaction. This could have been improved by having an assistant or using a n airlock system.
By using these improvements in my investigation I could improve the accuracy of the results.