Above this temperature the enzyme structure begins to break down (denature) and intermolecular bonds are broken as the enzyme molecules gain more kinetic energy.
I predict the enzymes will work best at 40 ˚C because the enzymes in animal bodies work best at 37˚C, as there more energy causing the enzymes split up the starch faster. Amylase enzymes at 0˚C will not have enough energy for the starch to enter the enzyme in order to make a reaction and will not work. This is why the starting temperature is 20˚C.
Biological Knowledge
An enzyme is a protein molecule which speeds up chemical reactions. Enzymes are known as Biological catalysts as they speed up reactions in living systems. Within the enzyme there is the active site, which has a specific shape where reactions occur.
The substrate molecule will join the enzyme (protien) molecule to create the product molecule. The higher the temperature the more kentic enegery there will be- too high a temperature can denature a enzyme. The kentic enegy will cause the molecules to have more free movement and cause more collisions. When the substarte molecule and enzyme molecules collide they create an
Enzyme-Substrate Complex where reactions occur.
Temperature affects enzymes, low temperature causes the enzymes to have little or no kentic energy, causing the molecules to move slower resulting in less collision and a low rate of reaction. Increasing the temperature increases the kinetic energy of the enzyme and substrate molecules so that they move faster and are more likely to collide.
Increasing the temperature increases the rate of the reaction up to a certain temperature; this temperature is known as the enzyme’s optimum temperature, different enzymes have different optimum temperatures. If the temperature is increased beyond the optimum the enzyme has so much kinetic energy that the bonds holding the enzyme molecule together start to vibrate and eventually break. The enzyme loses its specific shape so that the substrate no longer fits in to the active site. We say that the enzyme is denatured.
Measurements:
We used 6 different temperatures in this expirment:
25˚C (24˚C),30˚C (29˚C), 35˚C,40˚C,45˚C (44˚C) and 50˚C (49˚C).
Six temperatures were needed so we could compare the affect and produce a graph. We chose these temperates because they fall on what we belive to be the optimum temperature. The procedure was repeated three times to ensure the results would be reliable and so we could identify any anomalous results.
Rate of
Reaction(s)
X1000
Temperature ˚C
Method
Apparatus/Chemicals:
- Six waterbaths
- Beakers
-
Syringes (5 cm3) (5ml)
- Spotting Tile
- Stop Clock
- Saftey goggles
- Dropper (pipette)
- 1% Starch suspension
- 0.1% Amylase solution
- Iodine Solution
Procedure:
- Switch on the water baths and allow them to reach the temperatures needed.
- Place amylase in a beaker and starch in a different beaker into each water bath. The water baths will have different temperatures.
-
Using syringes to measure the volumes, place 5 cm3 starch suspension in one beaker and 5cm3 of Amylase in a separate beaker. Make sure you use different syringes so there is no coss-contamination of substances.
- Place one drop of iodine in each depression of the spotting tiles using a pipette. Saftey goggles should be worn as iodine is dangerous to the eyes.
- Pour the contents of one beaker i.e Pour the starch into the amylase, then swirl the liquid to ensure thorough mixing.
- Straight after this, start the stop clock and drop one drop of the mixture into the first depression of the spotting tile.
- Leave the stop clock running and every 30 seconds, drop one drop of the starch/amylase solution into successive depressions of the spotting tile.
- Observe the colours in the spotting tile and when the solution no longer goes blue/black stop the clock and note the time.
As the enzyme breaks down the starch it changes from starch to molecules. If starch is still present the iodine will turn a blue/black colour which shows that the amylase has not completely broken up the starch. Once the starch is broken the solution will no longer change colour. The 30 second intervals will leave 5˚C intervals between each and allow the amylase to break up the starch more and more. Water baths are used in this expirment to keep the amylase and starch solutions are their desired temperatures. This is done by heating the water bath to its desired temperature and placing the different solutions inside. Without the water baths we could not have six different temperatures and could not test the effect of temperature on the enzyme, amylase.
Results
Time for starch to be broken down table
Interprectation
Trends:
As the temperature increases the rate of reaction increases up to a maximum value/rate and then it decreases.
For example at 24˚C the rate of reaction per second (X1000) is 1.10. As temperature increased to the optimum temperature of 40˚C the rate of reaction increased to 3.33, beyond the optimum the rate of reaction fell to 1.17 at 49˚C.
These results support the hypothesis which stated that the rate of reaction will increase, but will only occur up to a certain point and temperature or the enzyme will become denatured- causing the rate to decrease drastically.
From the graph the optimum temperature is identified as 40˚C.
Scientific Explaination:
At a low temperature the enzymes are less active because of a lack in kenetic energy, less movement, a slower reaction and fewer collisions.
As temperature increases the enzyme has more kenetic energy, more collions, more reaction and this continues to the optimum temperature, which in this experiment was 40˚C.
Beyond the optimum temperature the kenetic energy causes vibrations as the bonds in the enzyme brech. The active site changes shape and the enzyme is denatured, this causes the reaction to stop.
Sources of Error
This procedure was suitable because the iodine test produced results that were easily observed to determine the rate of reaction and results were as expected. The set of results in the replicas are similar but not identical, this is due to sources of error.
For example:
- Differences in drop size therefore more/less iodine mixture added will affect the colour.
- Timimng. It was difficult to start the clock/timer and mix the solutuion at the same time
- It is difficult to judge and point due to simiular colour in the last few spots, it was personal interpretations of the colour.
Improvments
- Use a syringe instead of a dropper to produce equal volume (0.1) ml.
- Work in pairs to improve the timing- one person mixes, one person sets the clock.
- Use spotting tiles of the same shade (all white or all cream) so the colours will be the same.
- Or use a colourmeter machine to judge the colours.
Anomalous Results
An odd result was 24˚C - 660˚C. It was faster than the others due to the possiblity that there was too little starch or too much enzyme.
At 44˚C - 870˚C is slower than the others, this may be because there is too much start or too little enzyme.
Both of these are accurate for measurment error.
