Section C: Give a short answer to the question given below.
29.a. With the help of an activity, explain the action of saliva on the food we eat.
Experiment demonstrating the action of saliva.
Aim: To study the activity of saliva on starch present in food.
Materials required:
- Two test tubes
- Boiled rice
- Dilute iodine solution
- Water
Procedure:
- Take two test tubes. Label one test tube as A and another as B.
- Take a spoon of boiled rice and add it to the test tube labelled as A.
- Take another spoonful of boiled rice. Chew the boiled rice for 3 to 5 minutes.
- Add the chewed boiled rice to the test tube labelled B.
- Add 3 to 4 ml water in both test tubes.
- Then, add 2−3 drops of iodine solution in each test tube.
- Observe the colour change seen in both test tubes.
Observation:
A colour is produced in the test tube and is labelled A. A test tube labelled B shows .
Inference:
A colour change was observed in the test tube labelled A as the boiled rice contained . In the test tube B, there is no change in colour. The present in the saliva breaks down the starch into . Since no starch is present in the test tube after the treatment of boiled rice with saliva, there is no colour change to blue-black. Thus, saliva breaks down the starch to sugar as maltose.