Spitting Amylase

            In this experiment you will observe the action of the enzyme amylase on starch.  Amylase changes starch into a simpler form: the sugar maltose, which is soluble in water.  Amylase is present in our saliva, and begins to act on the starch in our food while still in the mouth.
            Iodine is a test reagent for the presence of starch.  When starch is present in a solution, the iodine with turn it from light purple to blue/black, depending on the concentration of starch.  As amylase acts on the starch, the solution should lighten in color.

Materials:

• Cornstarch
• Distilled water
• Saliva
• Iodine
• 15 mL conical tube
• Water bath (if available)
  
  Pre-lab:
              Make a 0.5% starch solution by mixing 1g of cornstarch with 200 mL of distilled water until dissolved.  Shake well before each use.
              Iodine may be Gram’s Iodine or commercial tincture of iodine and dilute 1:4.

Procedure:

1. Fill the 15 mL conical tube with 3 mL of  0.5% starch solution.
2. Add a drop of iodine to the starch solution (taking care to keep the iodine off the opening of the tube)
3. Carefully “spit” between 1 and 2 mL of saliva into the tube, cap and mix gently by inverting the tube 3 times.
4. Record your observation at this “initial time”.
5. Place the tubes in warm (370 C) water
6. Check the tube and record your results every five minutes for 15 minutes.

Data Table 1:  Amylase Activity on a Starch Solution

1. When the iodine indicator stays reddish-brown, what does that say about the starch content?

2. If the blue-black color in the starch lightens over time, what can you conclude about the amylase in the saliva?

3. Enzymes like amylase may be destroyed in an environment with an unfriendly pH or temperature.  Design an experiment to test the action of amylase in an acidic pH.

4. Research a testing method for maltose.  Design an experiment to test the end product of our “Spitting in Starch” solution.

Preparing a 0.5% starch solution

• Makes 200 mL; store at room temperature indefinitely

1. Dissolve 1 g. corn starch in 80 mL of distilled water
2. When dissolved, bring to volume of  200 mL
3. Shake well before each use.

Adapted from  “Amylase on starch lab” from http://sps.k12.ar.us/massengale/amylase_on_starch_lab.htm by DeAnn Campbell and Megan Waugh, Oklahoma City Community College, Biotechnology/Bioinformatics Discovery Project!