A. Digestion of Starch by Salivary amylase:-
1. 2 test tubes are taken with some water and is labeled. 2 tsp of boiled rice is added in one tube and 2 tsp of boiled rice that has been chewed for 2−3 minutes is added to another tube.
2. A few drops of iodine is added to both the tubes.
Results - The tube with the boiled rice turns blue due to the reaction of starch with iodine. The tube with the chewed rice does not change colour. This is because salivary amylase acts on the starch in the rice during chewing and breaks down the starch into smaller sugar units.
B. Effect of pH:-
1. Take 3 test tubes with 2 ml starch solution and label them. Add 1ml of saliva solution to each tube. Add 1ml each of water, NaOHsolution,anddil.HCl solution to the respective tubes.
2. After a few minutes, a few drops of iodine solution is added to each tube.
Results - The activity of salivary amylase is the best at pH of 6−7 with the highest at a pH of 6.8. So, it means that the activity of salivary amylase is good under acidic to neutral conditions. So, the blue colour will be more in the tube with the NaOH as there will be no activity of the salivary amylase on the starch solution. The blue colour will be light in the tube with water and a very little in the tube with dil.HCl. However, it will fade away soon and there will no colour. This is because the salivary amylase is active in acidic pH and so it will break down the starch to smaller glucose molecules.
C. Effect of temperature.
1. The test tubes are labeled and 2ml of saliva solution and 4 ml of starch solution is taken in each tube.
2. The test tubes are kept in water baths of 37°C,50°C, and one in boiling water. After a few minutes, the test tubes are removed and a few drops of Iodine is added.
Results - The activity of salivary amylase is maximum at a temperature of 32−37°C. At high temperature, the enzyme gets denatured and at lower temperatures, the enzyme is not active, so the enzyme activity does not occur. So, the test tube at 37°C turns blue first but eventually becomes colourless. The other test tubes have blue colored solutions.