The more successful the collisions are the faster the reaction.
The same can be said for reactions controlled by enzymes, but because enzymes are proteins if the temperature exceeds 50¦ C the enzyme will be denatured and will no longer work. For this reason few cells can tolerate temperatures higher than approximately 45¦ C.
Enzymes are specific in the reactions they catalyse, much more so than inorganic catalysts. Normally, a given enzyme will catalyse only one reaction, or type reaction.
This shows how the shape of an enzyme molecule could be very important if it has to fit the substances on which it acts. Above 50¦ C the shapes of enzymes are changed and the enzymes can no longer combine with the substances.
Starch + water - sugars
Prediction: I predict that the breakdown of starch will be quicker when the temperature is increased until it exceeds 40¦ C. Then the amylase will no longer catalyse the breakdown of starch.. This is because amylase is made up of protein molecules and therefore it is easily denatured by heat, losing itÆs shape and no longer able to combine with the starch. I think the rate of breakdown of the starch will increase until this point because the increase in temperature will supply the molecules with more energy to react, and then it will slow down and the rate of reaction will be a lot longer.
Dependant variable: rate of breakdown of starch, time
Independent variable: temperature of solution
control variable: volume of starch solution
volume of amylase solution
concentration of amylase solution
concentration of starch solution
amount of iodine
agitation
Apparatus:
Water bath
2 test tubes
2 spotting tiles
pipette
thermometer
test tube rack
iodine
amylase -3%
starch-1%
stop clock
glass rod
Plan:
Set the water bath to 40¦ C
using a measuring cylinder measure 10ml of starch from the same solution each time
Pour 10ml of starch into one test tube
Pour 5ml of amylase into another test tube
Put the test tubes into the water bath
Put a thermometer into the starch solution
Put 2 drops of iodine into each part of the spotting tile
When the temperature becomes constant mix the amylase with the starch and start the stop clock at the same time
stir twice with a stirring rod for equal agitation
stir the mixture twice with the glass stirring rod
Every 30seconds remove a small portion of the solution and put into a spotting tile dimple with iodine in
Record the time that the solution doesnÆt change the colour of the iodine
Repeat this at a range of different temperatures
use ice to reach a lower temperatures
change the temperature of the water bath
Repeat each temperature twice to get more accurate results
Results
temperature 14¦ C Time in minutes colour 1st experiment colour 2nd experiment
0 black black
0.30 black black
1 black black
1.30 black black
2 black black
2.30 black black
3 black black
3.30 black black
4 black black
4.30 black black
5 black black
5.30 black black
6 black black
6.30 black black
7 black black
7.30 black black
8 black black
8.30 black black
9 black black
9.30 black black
10 black/brown black/brown
10.30 black/brown black/brown
11 black/brown black/brown
11.30 black/brown brown
12 brown brown
Temperature 21¦ C time in minutes colour 1st experiment colour 2nd experiment
0 black black
0.30 black black
1 black black
1.30 black black
2 black black
2.30 black black
3 black black
3.30 black black
4 black black
4.30 black black
5 black/brown black
5.30 black/brown black/brown
6 black/brown brown
6.30 brown brown
7 brown brown
Temperature 28¦ C time in minutes colour 1st experiment colour 2nd experiment
0 black black
0.30 black black
1 black black
1.30 black black
2 black black/brown
2.30 black/brown black/brown
3 black/brown brown
3.30 brown brown
á
Temperature 37¦ C time in minutes colour 1st experiment colour 2nd experiment
0 black black
0.30 black/brown black/brown
1 brown brown
Because this reaction was so quick I took results at more regular intervals of 10 seconds. Time in seconds colour 1st experiment colour 2nd experiment
0 black black
10 black black
20 black/brown black
30 brown black
40 brown brown
50 brown brown
Temperature 45¦ C time in seconds colour 1st experiment colour 2nd experiment
0 black black
10 black black
20 black black
30 black black
40 black black/brown
50 black black/brown
60 black black/brown
1min 10 black/brown black/brown
1min 20 black/brown brown
1min 30 brown brown
Average time taken for the breakdown of the starch á time taken for breakdown of starch (min)
temperature ¦ C 1st experiment 2nd experiment average
14 12.00 11.30 11.45
21 6.00 6.30 6.15
28 3.00 3.30 3.15
37 0.30 0.40 0.35
44 1.30 1.20 1.25
My graph shows that I have no anomalous results and they all follow a smooth curve.
My graph shows that there is an optimum temperature . The first graph is a curve with all points in a place I would expect them to be.
Analysis.
My first graph shows the time taken for the amylase to break down the starch at a range of temperatures.
The graph is a curve showing that at 14¦ C the breakdown of starch to take 11.30 min and 37¦ C to be the optimum temperature taking 0.35 minutes to breakdown the starch, after this temperature the enzyme is denatured. The proteins structure unravels, which changes the shape of the molecule, and exposes the inner cells of the protein to the killing temperature. The gradient shows that the enzyme is not working as efficiently as it could and therefore needs a greater amount of time to breakdown the starch.
This supports my prediction that amylase works best at temperatures slightly below 40¦ C.
My graph showing the rate of reaction between the starch and the amylase shows that as the temperature increases to 40¦ C the rate of reaction also increases and that as the temperature increases above 40¦ C the rate of reaction will decrease rapidly.
The peak in the rate of reaction is 37¦ C which is the best temperature for efficient use of amylase. The reason for the decrease in rate of reaction after 37¦ C is the enzyme is damaged.
Evaluation
My results proved my prediction to be correct. The breakdown of starch is quicker as the temperature increases until the optimum temperature after which it begins to slow down.
I think my results were sufficient to support a firm conclusion, but if I had the chance to investigate further the effect of temperature on the breakdown of starch I would take more results focusing on the higher temperatures and try to pinpoint the optimum temperature.