Prediction
It is expected that as the temperature increases, starch molecules will be broken down more quickly. However, the temp may reach a point the enzyme de-natures, or stops working. This can be expected to be above 37.5ºC. (At this temp enzymes and other biological materials may become damaged/ destroyed). The activation site may become wobble-like, and unusable, so stopping starch molecules from being broken up (see diagram).
But why does increasing the heat up to 37.5ºC decrease the time taken for starch molecules to be broken down?
It is expected that as the starch molecules and the activation site of the enzyme receive more energy, they will bounce around faster, and are more likely to crash into each other, they will meet faster and break each other up.
- enzymes become hot, but no more than 37.5ºC.
The energised molecules and enzymes move around much faster with heat.
- the temperature is more than 37.5ºC!
Procedure
Key variable: temperature
Measured variable: time taken for starch to be broken down.
Controlled variable: quantity
Salinity
Equipment:
1 x ice bucket
Lab temp
Water baths (1x 50ºC and 1x 60ºC)
Thermometer
Stop watch
Pipettes
1 ml Amylase to
5 ml starch
Flow chart
Attain temp
Mix starch any amylase
Start watch
Every 15secs drop in amylase + starch in iodine
Record data
When the sample turns from black to transparent, it means that there is no starch left in the solution. (iodine turns black when starch is present)
Table of results
Evaluation
The graph is a curve shape. This shows that when the temperature is lower, the time taken for the enzymes to break down starch is much longer. However, as the temperature increases, the speed at which the starch is broken down becomes faster. (See diagram for explanation). The temperature finally reaches a peak where the reaction becomes slower. This is where the curve begins to rise again, around 40ºC, as predicted.
There is an amomalous result on the graph. The time taken for the starch to be broken up at 60ºC-the result does not fit in with the rest of the resluts. The reason for this amomalous result could be because the temp was not measured every 20 seconds exactly, and the mixture was given a tiny bit more extra time than the others. To test whether this result is really anomalous, the experiment must be repeated.
Our main procedural problem was when our first attempt at the experiment failed (using 1ml amylase to 10 ml starch). This was because the starch amount was too much- the more starch, the more time it took for the reaction to occur.
To research more in to this topic, other experiments could be done. Such as, does the enzyme reach a point that’s so cold it simply won’t react with the starch? Or, does the same curve appear in a graph of a different enzyme, such as protease or lipase.
