SALIVARY AMYLASE for 5Eme

Enzymes: Nature’s little workers

Enzymes are used in biological processes. An enzyme, amylase, is found in human saliva and in secretions made by the pancreas. Starch is a large molecule (a polysaccharide) found in many foods (e.g. bread, potatoes, rice and pasta). We need to break the starch molecules down into glucose molecules before we can absorb them into the blood. This investigation will compare the effect of salivary amylase, hydrochloric acid and water on starch.

Materials Safety spectacles or goggles, Water bath at 100°C, Sodium hydrogen carbonate powder, 6 test tubes + stand, Clean elastic band, Spatula, Marker pen, 3 small beakers, 3 Glucose testing strips, 2 x 5cm3 syringes, Wash bottle of distilled water, Scissors, Wooden test tube holder, 10cm3 solution 1% starch, Dropping bottle iodine solution Electronic heater, Dropping bottle hydrochloric acid,

Method WARNING: Hydrochloric acid is corrosive tie back long hair, wear safety spectacles. 1. Place a beaker of tap water on to the heater and bring it to the boil.

2. Label six test tubes 1 to 6.

3. Collect 1cm saliva in a small beaker (chewing on a clean rubber band helps)

4. Add 2cm3 water to tube 1 and 4 Add 2cm3 HCl to tube 2 and 5 Add 2cm3 saliva to tube 3 and 6

5. Leave tubes 1, 2 and 3 at room temperature Place tubes 4, 5 and 6 in boiling water for 2 minutes.

6. Using the syringe add 2cm3 starch to each tube and leave them for 10 minutes.

Tube Starch Liquid Temperature / cm3 / cm3 / °C 1 2 2 (water) 20 2 2 2 (HCl) 20 3 2 2 (saliva) 20 4 2 2 (water) 100 5 2 2 (HCl) 100 6 2 2 (saliva) 100

7. After 10 min remove the tubes from the boiling water neutralise the acid in tubes 2 and 5 by adding sodium hydrogen carbonate powder. The acid is neutralised when then powder no longer effervesces.

8. Cut 3 glucose testing strips in half to make 6 strips. Test each tube for glucose using a testing strip. Record your results. Add a few drops of iodine solution to each tube to test for starch. Record your results.

Discussion  Compare the effect of saliva and hydrochloric acid on starch.  What was the point of adding water to tubes 1 and 4?  What is a catalyst and how does the term apply to this investigation?  Hydrochloric acid is also produced naturally by the stomach. Why is it not a suitable liquid for breaking down starch in the digestive system? PPBilliet 6/05/18