Saliva and starch digestion
Introduction
Starch is a polysaccharide which has to be broken down into free sugar molecules before absorption takes place.
Absorption is defined as the event during which small molecular forms are absorbed through cells of a digestive system and pass into nearby blood or lymphatic vessels.
The role of amylase is to temporarily hold the starch in its active site and put stress on the covalent bonds that bind the glucose molecules together within the polysaccharide. When these bonds are stressed, it is more likely that the surrounding thermal energy will provide enough molecular motion to break the bonds.
The purpose of this experiment is to:
test the hypothesis that saliva contains an enzyme which breaks down starch to sugar;
investigate the properties of the enzyme and the conditions under which it works most effectively.
Data collection and processing
1. The effect of starch on iodine solution
Test tube | Content | Observations | Conclusions |
I | 5 ml 1% starch solution + 5 drops iodine solution | The mixture becomes pale blue in colour. | Iodine causes that starch turns blue / purple. |
II | 5 ml water + 5 drops iodine solution | A pale yellow colour is obtained. |
2. The effect of saliva on starch
Test tube | Content | Observations | Conclusions |
I | 5 ml 1% starch solution + 1m saliva + 5 drops iodine solution | The mixture becomes yellow in colour. | Saliva contains an enzyme, amylase, which digests starch to disaccharides. Polysaccharides are no longer present. Lugol's solution turns blue only when starch is present. |
II | 5 ml water + 5 drops iodine solution | The mixtures turns dark blue. |
3. The effect of boiled saliva on starch
Test tube | Content | Observations | Conclusions |
I | 5 ml 1% starch solution + 1m saliva + 5 drops iodine solution | The mixture becomes dark blue in... | |