Salivary amylase: This is produced by the salivary glands and acts in the mouth to break down long chains of starch in food into smaller chains of maltose. The solution is very slightly alkaline because the mouth is on the alkaline side of neutral.
(A Level Biology, W D Phillips and H J Chilton)
The solution is bought in powder form from a catalogue; the catalogue states that it has an optimum pH of 5.5-8.5.
(Phillip Harris International)
Bacterial amylase: Bacteria will live in most conditions because they need to reproduce so adapt to different environments well. They have to respire to reproduce and they can respire either by anaerobic respiration (GLUCOSE → LACTIC ACID + ENERGY) or aerobic respiration (GLUCOSE + OXYGEN → CARBON DIOXIDE + WATER + ENERGY). So when bacteria respire they produce lactic acid or carbon dioxide (the carbon dioxide makes carbonic acid when it reacts with water), either way of respiring produces an acidic environment. Because of this bacterial amylase will have a slightly acidic pH.
The school buys the bacterial amylase in powder form a catalogue; the catalogue states that it will have an optimum pH between 4.5 and 6.5.
(Phillip Harris International)
Risk assessment:
The CLEAPASS HAZCARDS state that amylase is a low hazard substance and it doesn’t offer any significant risk such as irritation.
To reduce risks:
- Use lowest concentrations possible
- Reduce risk of skin contact by wearing disposable gloves
- Wear eye protection
All enzymes are proteins and may produce allergic reactions. It is best to handle all enzymes as a potential allergen and to minimize skin contact and inhalation.
Preliminary Experiment
I spent time investigating how I was going carry out my experiment by altering concentrations and volumes of solutions. I first carried out my experiment by putting 1cm³ of the pH 10 buffer solution, 1cm³ of 1% starch solution and 1cm³ of the amylase in a test tube and every 15 seconds put a drop of the solution in a spotting tile with iodine and watching for an unchanged colour of the iodine, but within 10 minutes no reaction had happened so I decided to dilute the starch solution to 0.1% concentration and repeated the experiment as before; still I did not see a reaction happen in 10 minutes. I then decided to add 2cm³ of the amylase to 1cm³ of the 0.1% starch solution and 3cm³ of the pH 10 buffer. This time I tested that the pH was actually making the solution the correct pH so I used pH test strips. When I had added all the solutions together I dipped a pH test strip in the solution and checked that the colour on the strip was actually pH 10 and it was so I knew that these were the correct volumes and concentrations I should use.
Apparatus
Spotting tile, range of pH buffers (pH 3, 4 ,6 ,7.6, 8 , 9, 10), 3 test tubes, 1% salivary solution and 1% bacterial amylase solution, 0.1% starch solution, stop watch, pipettes, iodine, test tube rack.
Method
1/ Dilute the starch solution from 1% to 0.1% by adding 9cm³ of distilled water to every 1cm³ of starch solution.
2/ Add 1cm³ of the 0.1% starch solution to 3cm³ of chosen pH buffer to a test tube.
3/ Add 2cm³ of salivary amylase to the test tube and start the stop watch.
4/ Every 15 seconds take a drop of the solution using a pipette and add it to a drop of iodine in a spotting tile.
5/ Keep taking samples every 15 seconds until the sample no longer turns blue/black (this means there is starch present) and it does not change the colour of the iodine (this means that the starch has being digested and is no longer present).
6/ Repeat every pH 3 times so I have enough results to pick out incorrect results. Carry out the experiment with 7 different pH buffers, and also carry out the whole experiment also using bacterial amylase.
7/ Record all results and plot graph using the averaged results.
Results
Salivary amylase
