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Investigating the optimum pH at which salivary and bacterial amylase digest starch in to maltose.

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Kerry Nicholls Aim: To investigate the optimum pH at which salivary and bacterial amylase digest starch in to maltose. Prediction: I predict that Salivary amylase will work best at pH8 as this is the pH of the mouth and so an enzyme that works in the mouth will have an optimum pH of the environment where it works. I predict that Bacterial amylase will work best at a pH 5 or 6 as bacteria usually live in slightly acidic conditions. Biological knowledge: The effect of pH on enzyme activity: Most enzymes have a characteristic pH at which they function most efficiently, this I known as their optimum pH. Changes in pH affect the ionisation of the amino acid side group of the enzyme, this affects enzymes tertiary structure which means the active site is changed, and this in turn affects the efficiency at which the enzyme forms enzyme substrate complexes. At extreme pH's the enzyme may become denatured, this is when the active sites complementary shape is lost and so no enzyme substrate complexes can be made, denaturation is permanent. ...read more.


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 1cm� of the pH 10 buffer solution, 1cm� of 1% starch solution and 1cm� of the amylase in a test tube and every 15 seconds put a drop of the solution in a spotting tile with iodine ...read more.


Method 1/ Dilute the starch solution from 1% to 0.1% by adding 9cm� of distilled water to every 1cm� of starch solution. 2/ Add 1cm� of the 0.1% starch solution to 3cm� of chosen pH buffer to a test tube. 3/ Add 2cm� 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 pH of buffer Time taken for starch to be digested Average time Repeat 1 Repeat 2 Repeat 3 ...read more.

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