My Prediction:
I think that the enzyme (lipase) will react fastest in a water bath, which is set at a temperature between 35˚C and 45˚C.
The Science behind my prediction:
I think lipase will work best at a temperature between 35˚C and 45˚C because most natural enzymes have an optimum temperature of approximately 40˚C. If the temperature used exceeds the optimum temperature then the length time taken for the lipase to change the solution back to the same colour as the solution inside the control tube will increase. If this temperature is too high then the enzyme (lipase) will begin to denature. On the other hand if the temperature is below the optimum temperature then the enzyme will again increase the time needed for the lipase to change the solution back to the same colour as the solution in the control tube, but the enzyme will not denature under extremely cold conditions. A substance, which is acted upon by an enzyme, is called its substrate (fats in this case). The active site of an enzyme is the region on the surface on the enzyme molecule where a substance molecule can attach itself. This is when the catalyst speeds up the reaction. The shape of the substrate molecule and the shape of the active site are complementary (fit into each other). As soon as the ‘enzyme-substrate complex’ has formed the products of the reaction are released and the enzyme is ready to accept another substrate molecule.
Apparatus List:
How to make this a fair investigation:
During this investigation there are many factors that could affect the overall results of the experiment, this would therefore make the test unfair. For the duration of this investigation I will only change one factor to make this a fair test, I will change the temperature of the water baths which will show me how the enzyme, lipase performs under various conditions. I will be required to reduce the effects of the following factors as they may influence a change in the results:
The concentration of solutions (Milk, Lipase, etc)
The amount of solution
The equipment used (Size shape etc)
To keep the previous list of factors, less of a problem and to create a fair test I will use the same concentration of solution and the same amounts of solution throughout the investigation. To keep the equipments size, shape, and surface area the same I will use the same equipment throughout the experiment and rinse thoroughly between each test. To prevent the use of mistakes in my investigation I will produce 4 repeats at each temperature. I will then find the average of the total list of results, which will provide me with more accurate results; this will also prevent any bias.
Method:
1). Carefully collect all of the equipment from the apparatus list, now set up the water baths at the required temperatures.
2). Secondly, add 2cm³ of milk and 1cm³ of phenol red into a test tube, this will now be used as the control tube.
3). Now, complete stage 1 again in another test tube, but this time add an additional 3 drops of Sodium Carbonate in to the test tube.
4). Now carefully add 1cm³ of lipase into another test tube, now move these test tubes from the test tube holder to the water bath which is set at the required temperature.
5). Wait for approximately 5 minutes then pour the lipase from the second test tube into the first test tube containing Milk, Phenol Red, and Sodium Carbonate.
6). Start the stopwatch / clock as soon as the two solutions meet, next you check the solution every minute.
7). Once the solution changes to the same colour as the solution in the control tube you must stop the stopwatch / clock and record the results into the results table.
8). Finally repeat this experiment again starting from stage (2) for the following temperatures; 20˚C, 30˚C, 40˚C, 50˚C, 60˚C, 80˚C.
ALWAYS WEAR GOGGLES AND TAKE CARE WHEN HANDLING SOLUTIONS.
Conclusion:
From my graph I have found that as the temperature of the water bath increases so does the rate of reaction of the lipase under these conditions (between the points of 23.25˚C and 49.16˚C). But after the temperature used exceeds optimum temperature for lipase to react the graph begins to dip this shows that lipase performs best under approximately 50˚C conditions (this is shown by the points after 49.16˚C).
Analysis:
The results I have produced in relation to my prediction are fairly accurate, as in my prediction I explained that I thought that the optimum temperature would be between 35˚C and 45˚C. Although as a result of my investigation I found that the actual optimum temperature was closer to 50˚C.
During my investigation I have discovered that the lipase is a digestive enzyme, which breaks down fats into Glycerol and fatty acids. When the lipase works against the artificially alkali solution it begins to produce fatty acids, which begin to neutralise the Milk, Phenol Red, and Sodium Carbonate solution. This reaction is show by the indicator (Phenol Red) as it changes from an alkali (Pink colour) to a neutral (Orange colour), which is the same colour as the colour control tube, which contained no artificial alkali solution. Therefore the solution within the colour control tube is neutral (Orange in colour).
I also discovered that the substance, which is acted upon by an enzyme, is called its substrate. The active site of an enzyme is the region on the surface on the enzyme molecule where a substance molecule can attach itself. The shape of the substrate molecule and the shape of the active site are complementary (fit into each other). As soon as the ‘enzyme-substrate complex’ has formed the products of the reaction are released and the enzyme is ready to accept another substrate molecule. This was shown as the reaction took place inside the test tubes at the various speeds. The speed of the reaction would depend on how quickly the ‘enzyme-substrate complex’ is produced and how quickly it can move on to another substrate molecule.
Evaluation:
I thought that the results that I found were fairly accurate to the same degree of accuracy as the equipment, as the equipment that was available was not the most accurate. So this is one of the factors that I would change if I were to repeat this experiment or a similar experiment in the future. I would also use more accurate water baths as the available electrical waters are well known for their inaccurate readings. I would also increase the amount of experiments taken at each temperature and the amount of temperatures tested overall. I believe that the final factor that I could change that would increase the accuracy of my results is that if I were to have a longer time to conduct the experiment I would complete the experiment one at a time which would reduce the amount of human error made. All of the results that I have found and produced have all fitted into the pattern that I would have expected before the initial investigation.
