Table of Contents
Experiment- Investigating the Digestive Action of Saliva on Starch
Materials Required-
- Two test tubes (labelled ‘A’ and ‘B’)
- Boiled rice
- Iodine solution
- Water
- Timer or stopwatch
Procedure-
- Take two test tubes and label them ‘A’ and ‘B.’
- In test tube ‘A,’ place one teaspoonful of boiled rice.
- In test tube ‘B,’ put one teaspoonful of boiled rice, but before adding it, chew the rice in your mouth for 3 to 5 minutes.
- Add 3 to 4 mL of water to both test tubes.
- To each test tube, add 2 to 3 drops of iodine solution.
- Observe and record any changes in colour that occur.
Explanation-
- This experiment is designed to investigate how saliva, which contains the enzyme amylase, breaks down starch into simpler sugars.
- In test tube ‘A,’ where unchewed boiled rice is placed, you will likely observe that the iodine solution remains its characteristic dark brown or bluish-black colour. This colour change indicates the presence of starch in the rice.
- In test tube ‘B,’ where you placed chewed rice, you may notice that the iodine solution changes to a lighter colour or becomes clear. This change in colour indicates that the starch in the rice has been partially or completely broken down into simpler sugars due to the action of saliva.
Why the Colour Change Occurs-
- Iodine solution turns dark brown or bluish-black in the presence of starch. Starch is a complex carbohydrate made up of long chains of glucose molecules.
- Saliva contains the enzyme amylase, which starts the process of starch digestion by breaking down the long starch molecules into shorter chains of glucose (maltose). This is the initial step in the conversion of starch into simpler sugars.
- When you chewed the rice in test tube ‘B,’ your saliva mixed with it, and amylase in your saliva began breaking down the starch in the rice.
- As a result of this digestion, the iodine solution in test tube ‘B’ no longer turns dark blue-black because the starch in the chewed rice has been partially converted into simpler sugars. The colour change indicates the presence of these simpler sugars.
This experiment demonstrates the digestive action of saliva on starch and provides a practical illustration of the initial stages of carbohydrate digestion in the mouth. It’s an example of how the body’s enzymes play a crucial role in breaking down complex nutrients into forms that can be absorbed and used by the body.
Chapter 2 – NUTRITION IN ANIMALS -Class 7 – Complete Notes
Also Check – Nutrition in Animals – Definition and Explanation of Important Keywords
Also Check – Activity -Arrangement of teeth and different type of teeth – Class 7
Also Check – Activity – Regions of the tongue for different tastes- Class 7
