- They then repeated the experiment at the different pHs’.
- They did the experiment 3 times for each pH
Aim
Sam and Sarah planned to discover the effects of pH on the activity of the enzyme amylase which breaks down starch into sugar.
Prediction
I predict that the pH that the enzyme will work best at is 8 because amylase is mostly found in the mouth and salivary glands. This area is normally slightly alkaline, so the pH that this enzyme would most likely work best at would be 8.
Table
Analysis
When the pH of the solution becomes too acidic/alkaline, the time that the amylase takes to break down the starch increases. Amylase is a breaker enzyme and therefore uses the lock and key method to break down starch into sugar. Starch (the substrate) fits perfectly into the amylases active site and from here can be broken down into sugar (There is a more detailed explanation in the diagram below).
When the enzyme is placed in too acidic/alkaline conditions the active site denatures and the substrate no longer fits.
My prediction was supported by my graph (on the opposite page) the lowest point on the graph shows the optimum pH which in this case was 8. Therefore my prediction was correct.
Evaluation
This experiment was reliable in the view that there only appeared to be 1 anomalous result which was 7.6 (min) at a pH 6 when it should’ve been 6.1 (min) this is shown on the line graph. This result may have been wrong because the experiment didn’t utilize tools which were accurate enough such as: -
- The universal indicator is not very accurate
- It may not have been timed exactly every 30 seconds
- Not all of the drops of Iodine may have been the same
- It’s quite difficult to tell whether the iodine has stopped turning black
- Some starch may have been left in the test tube
- The pipette may not have been accurate enough
The experiment could be improved by using the above to make the experiment a lot more precise. The above can be changed to the following:-
- A pH metre could be used
- The Iodine could be measured by a graduated pipette or a syringe
- The starch and amylase solution can also be measured by a graduated pipette or a syringe
- A colorimeter could be used
The table (on page 1) shows that each time the experiment was performed the amount of time differed i.e. for pH 2: -
This also showed that the experiment may not be very reliable, the actual average wasn’t 15.7 it was actually 15.66* but we rounded it to 15.7. This may have affected the accuracy of the end results i.e. the graph. The fact that the gap between the two numbers was so large (2 minutes) also shows how unreliable the experiment is.
Sam and Sarah could extend this experiment by using all of the pHs’ in the experiment not just the even numbers such as pH 1, 3, 5, 7, 9 etc. They could also extend the experiment further and investigate all pHs’ from 7.0 to 9.0 e.g. 7.1, 7.7, 8.3 and 8.9 (obviously with the other pHs’ in between) This will show whether the optimum pH is really 8.0 (it could be 7.9 or 8.1).
I don’t think that the evidence from this experiment is accurate enough to support a conclusion for the previously mentioned reasons. I think that is extremely likely to make mistakes, like I said beforehand the average wasn’t 15.7 for that particular pH, this may have made major differences to a conclusion.
