Effect of pH on the action of amylase.

Aim: To Study The Effect of Different pH on the Activity of Salivary Amylase on Starch

Enzymes are biocatalyst that are involved in various metabolic reactions in a living system. All enzymes are proteins chemically, and they remain unchanged at the end of a reaction.

The optimum pH for the enzymatic activity of salivary amylase ranges from 6 to 7. Above and below this range, the reaction rate reduces as enzymes get denaturated. The enzyme salivary amylase is most active at pH 6.8.  Our stomach has high level of acidity which causes the salivary amylase to denature and change its shape. So the salivary amylase does not function once it enters the stomach.

Materials Required

Three series of test tubes having iodine solution in each, test tubes,

• 1.     Ph tablets of 5, 6.8 and 8
• 2.     Beaker containing water with thermometer
• 3.     15 ml 1% starch solution + 3 ml 1% nacl
• 4.     Saliva solution
• 5.     Droppers
• 6.     Bunsen burner
• 7.     Wire gauze

Procedure:

1.     Take a beaker containing 15 ml of 1% starch solution + 3 ml of 1% NaCl solution.

2.     Divide and pour this solution into three test tubes and mark them as A, B and C.

3.     Add pH tablet 5 into test tube A, pH tablet 6.8 into test tube B and pH tablet 8 into test tube C.

4.     Now transfer experimental tube A, B and C into a beaker containing water and a thermometer for recording temperature.

5.     Temperature of this beaker is to be maintained at 37°C.

6.     Using a dropper, take 3 ml saliva solution and add 1 ml of solution to each of the three test tubes.

7.     Immediately using a dropper, take few drops from experimental tube A and transfer this into the first series of test tubes having iodine solution.
8.     Similarly, do the same procedure for test tube B and test tube C and transfer the solution into second and third series of test tubes having iodine solution.
9.     Note this time as zero minute reading.
10.After an interval of 2 minutes, again take a drop from each tube and add to the iodine tubes and note the change in colour of iodine.

11. Keep on repeating the experiment at an interval of every 2 minutes till colour of iodine does not change.

Results

pH 5 is acidic and pH 8 is alkaline, therefore salivary amylase did not act in these tubes. Whereas, the enzyme acted in the tube with pH 6.8 (i.e., slightly acidic) and digested the starch.