Equipment
18 boiling tubes
25cm cubed measuring cylinder
2 sachets of gelatin granules
500cm cubed hot water
Tripod
Gauze
Bunsen burner
Stirring rod
Blender
Syve
Water baths
Ice
Design of Experiment
The experiment will be started my creating gelatin. This is going to be done by added two sachets of gelatine powder with 500cm cubed of hot water which will be heated by a Bunsen burner. Once the powder has mixed with the water and formed the smooth liquid the gelatin will be placed in boiling tubes. 15 boiling tubes will be used and 25cm cubed will be poured into each after being carefully and accurately measured in a measuring cylinder. The gelatin will then be left in the boiling tubes for 24 hours in a room, which will be at an average temperature of 20 degrees Celsius. It doesn’t matter if the temperature of the room in not constant at this point as long as all the tubes are in the same temperature.
While the gelatin is setting in the boiling tubes pineapple juice will be extracted from the pineapple. Chopping up the pineapple into small pieces then placed in a food blender will do this. The juice produced will then be placed into a cive to remove all the remaining lumps of pineapple. The pineapple juice will then be stored in the same room as the gelatine for 24 hours.
After 24 hours 5cm cubed of the pineapple juice will measured for each of the boiling tubes but the juice measured out will be kept in separate boiling tubes to that of the gelatin.
The pineapple juice will be heated at 5 different temperatures so three boiling tubes containing 5cm cubed of pineapple juice will be kept at each of the five temperatures. The temperatures, which are going to be used, are 0, 20, 35, 50 and 70 degrees Celsius. The temperatures, which exceed 20, will be heated in water baths until they reach their temperature then will be timed 2 minutes from when they reach their temperature. The tubes will then be removed and placed in a bath of ice until the temperature of the juice lowers to 20 degrees Celsius.
The pineapple juice will then be added to the gelatin which will be in separate boiling tubes and the pineapple juice will be left with the gelatin for a further 24 hours.
The reason for heating the pineapple on its own is because if the gelatin was to be heated as well it would melt and turn back into a liquid, which would mean the gelatin, and juice would mix together making the experiment unfair and inaccurate.
Before doing this experiment preliminary tests have been done. The first test was to see if the concentrating of the jelly affected the way in which the bromelain broke down the protein. The experiment showed the original concentration was not enough as the gelatin did not set hard enough so we done some more tests to find a concentration which would work the best. It was found that one sachet of gelatin powder with 250cm cubed of water was perfect. Both theses quantities were then doubles to obtain enough gelatin for 15 test tubes.
A second preliminary experiment was done to see if the volume of the pineapple juice added to the gelatin affected the results. It clearly showed that as more juice was added, more gelatin was broken down. Once carrying out this experiment I decided that 5cm cubed of pineapple juice was a suitable a sufficient amount to place with 25cm cubed of gelatin.
After the 24 hours of the pineapple juice being in the boiling tube with the gelatin, the liquid will be poured out of the boiling tube into a measuring cylinder and the amount of liquid obtained will be measured. This measurement will then be used to minus 5cm cubed from. This will then show how much of the gelatin has been broken down as it will be the extra liquid, which has been produced.
From the results it will then be clear if the temperature has affected the process and if it has by how much.
Changing The Manipulated Variable
The experiment, which is going to be carried out, is going to be measured by recording how much liquid will be put in compared to the amount of liquid after the 2 days. In all of the tubes will be 5cm cubed of liquid at the beginning, which will be the pineapple juice. After 24 hour the amount of liquid will be measured again and see how much of the gelatin has been broken down.
The liquid taken out at the end of the 48 hours will be measured carefully by a 25cm cubed measuring cylinder then the difference between that value and the original 5cm cubed will give the amount o gelatine which has been broken down.
The liquid will be measured to an accuracy of 1mm cubed throughout the experiment.
The factor of the experiment, which will be changed, is the temperature, which the pineapple juice is heated to before being cooled and placed with the gelatin. That is what will be altered so that it can be seen whether the temperature affects the amount of gelatin, which is broken down. The temperatures will be altered using water baths and the water baths will be set at certain temperatures, and ice to give the temperature required. The temperature will be measured using a thermometer, which will measure to an accuracy of 1 degree Celsius.
Since 3 boiling tubes with pineapple juice and gelatine will be used for each temperature an average of these three readings will be used when plotting a graph or working out percentage changes.
When the boiling tubes are left for the 48 hours they will be left in a room, which has a rough temperature of 20 degrees Celsius. The temperature of the room may change but that does not matter as long as all the tubes are in the same temperature to keep the experiment fair.
Maintaining Most Or All Other Features Constant
All environmental conditionals will be the same for all of the boiling tubes as they will all be situated in the same room. The room will be kept at a temperature at roughly 20 degree Celsius and this will be done by use of radiators in the room. The temperature of the room doesn’t matter too much as long as all the tubes are kept the same so none of the tests will be unfair or inaccurate.
A control for this experiment will be the 3 tubes, which are kept at 20 degree Celsius, which in this experiment will be classed as normal room temperature. By doing preliminary tests it is known what result should be obtained when left at this room temperature so this will indicate if the experiment has worked successfully
The dependent variable in this experiment is temperature as this is what is going to be changed in the experiment to show that temperature affects the way in which enzymes break down the peptide bonds of protein.
Prediction
From previous experiments I have done in the past, it has been found that the optimum temperature of the enzymes was in the region of 37 degree Celsius and once the temperature increased above that temperature the rate of reaction would decrease hence meaning in this case that less of the peptide bonds will be broken down.
Bibliography
Biology principles and processes Michael Roberts
Encarta Microsoft
Britannica
Bromelain Ron Kennedy
Enzymes
Bromelain www.mothernature.com/ency/supp/bromelain.asp
