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