Variable:
Temperature: You must control the temperature because if you do the investigation twice then you must make it a fair test. Once if the temperature is 2o°C the amylase and starch will move at normal speed but if you do it again and you find the temperature at 22°C not only will it not be a fair test but the starch and amylase molecules will move after, so they will collide more. I will control the temperature by using a ‘Thermostatically control water bath.’
Volume of amylase/starch: You must control the amount of starch and amylase you put in the solution, because if you put too much in then it would take longer for the solution to react because there is more to amylase and starch which will react together more slower. I will control the volume of amylase/starch by using a dropping pipette.
Concentration: This links into the volume of amylase/starch. I must control the concentration because it depends on the number of volume I put in, in each test tube. If there are more enzymes in 30°C than 50°C it will not be a fair test. I will control the concentration by making it myself.
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Iodine inhibitor: The amount of iodine is very important because if you put too much iodine in then instead of joining with the starch it will join together with the enzymes and then my experiment will go wrong. I will control the amount of iodine inhibitor by trying to use the same size of drops.
PH: The optimum ph for an enzyme depends on its site of action. For example: enzymes in the stomach have a finest ph of about 2 because the stomach is acidic but intestinal enzymes have a finest ph of about 7.5. I will control the ph by using a universal indicate.
Preliminary Method:
I carried out a preliminary experiment in order to get an accurate result:
Equipment:
The equipments I am going to use are:
Pipette
- Beaker (250ml),
- Measuring cylinder (50ml),
- Stopwatch,
- Thermometer,
- Kettle/hot water,
- Starch,
- Iodine,
- Amylase and Test tube.
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Method:
Step 1: Put water in a kettle and boil it fully.
Step 2: Pour the hot water carefully into a beaker and measure
with a thermometer the temperature you will need. If you would like a cooler temperature put ice in it to cool it down.
Step 3: Pour some starch with a pipette into a test tube.
Step 4: Add some iodine solution to the starch (two drops.)
Step 5: Put the test tube in the water carefully at the
temperature you are doing. Put the thermometer in the beaker of water.
Step 6: Add the amylase in the starch and at the same time press
start on the stopwatch.
Step 7: Wait until the solution has gone colour less. Then press
stop on the stopwatch.
Step 8: Do steps 1-7 at least twice to get a fair test.
Step 9: Do steps 1-8 at all these temperature: 30°C, 40°C, 50°C, 60°C and 65°C
Fair Test:
I will make this investigation a fair test, by having the same equipments; for example: if I have the temperature at 20°C I will try to not make it go up to even 22°C. Also what I will keep the same to make it a fair test is the starch and amylase. If I put 2.5cm³ of starch then I will put 2.5cm³ of amylase as well. Not only that but I will also keep the little thing the same like the same size beaker when I do each different temperature, keep the pipette in the right liquid (I want but the amylase pipette in the starch and the starch pipette in the amylase.) There is one thing I will change, and that is the different types of temperature from 20 all the way to 60°C.
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Safety:
One of my top priorities is safety in this investigation. It is important that I say how I will work safely during the practical.
Results:
This is a table to show the effect of temperature.
Temperature (°C) Time (s)
1st 2nd Average:
30 1080 1020 1050
40 30 22 26
50 35 40 37.5
60 20 35 18.5
65 15 25 20
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Analysing and Conclusion:
My graph shows a pattern; when the temperature increase the solution goes colour less more quickly. But I have one anomalies temperature, at 50°C. My graph shows the results that I have obtained through my investigation. My results show the higher the temperature the quicker the colour disappears. But when the temperature reaches 40C the solution denatures, this had happened because the temperature is reaching an optimum temperature, which means that the temperature is just perfect for the solution to go colourless the quickest time. I found a nice smooth pattern in my results but one-anomalies results.
I also found out one error, 40°C is meant to be the quickest
reaction but in my graph I found out that 60°C took the quickest time. I think this happened because I might have not read the stopwatch properly. This also could have happened because the enzymes might be genetically modified. Finally if I compare one of my results e.g. 30°C my first reading was 1080 but then my second reading came to be 1020. This could have happened because the temperature could have been going down as the stopwatch was continuing. I will now try and work out the rate of reaction: 1 / Average time = Rate of Reaction.
Temperature (°C) Time (s)
Average 1/Average time Rate of Reaction
30 1050 1 / 1050 0.0009
40 26 1 / 26 0.04
50 37.5 1 / 37.5 0.03
60 18.5 1 / 18.5 0.05
65 20 1 / 20 0.05
Evaluating:
I had one anomalies result, this could possible suggest,
because I could have read my reading incorrect or my reading of the temperature could have been incorrect. I felt that my investigation went quite well but sometimes my temperature was not very accurate.
One way of improving my experiment is that I could have
used a ‘Thermostatically control water bath.’ A second way of improving my experiment could have been contaminated due to the starch and amylase being mixed up with my pipettes. This use of the same equipment made my experiment contaminated. Finally, the last way of improving my experiment was, using two measuring cylinders so my investigation could have been fairer because by using one
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measuring cylinder there could still be starch in the cylinder even if I washed it out to put amylase in it. The results on my results table show one very anomalies results. At 50°C my results show 37.5s but at 60°C it shows at 18.5s. This could have happened because my temperature at 60°C could have gone down because I kept on adding more hot water.
To make my investigation a fairer test I could do some
different investigations on different types of enzymes such as, Plant enzymes, Fungai enzymes or Animal saliva (amylase.) This will show a fairer test on the rate of reaction with different types of enzymes and starch. A way I would carry out another methods would be:
Step 1: Put water in a Thermostatically control water bath and get the correct temperature you are looking for.
Step 2: Pour the hot water carefully into a beaker and double check that the reading on the thermometer is the same temperature in the water bath.
Step 3: Pour some starch with a pipette into a test tube.
Step 4: Add some iodine solution to the starch (two drops.)
Step 5: Add some amylase into another test tube and the put both tubes in the water carefully.
Step 6: Leave the test tubes in the water for about two minutes so they get use to the temperature
Step 7: Add the amylase in the starch and at the same time press
start on the stopwatch.
Step 8: Wait until the solution has gone colour less. Then press
stop on the stopwatch.
Step 9: Draw out a results table and write your results down while doing the experiment.
Step 10: Do steps 1-7 at least twice to get a fair test.
Step 11: Do steps 1-8 at the temperature you will like to do.
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By Rahul Malde 10e