Name ______________________________________ Period________ Date _____________
Cracker Lab
Digestion of starch normally begins in the mouth of humans where an enzyme, salivary amylase, is secreted,
catalyzing the break up of the starch. Starch is a polymer, made from thousands of sugar molecules joined
chemically into one giant chain-like molecule. Starch, a complex carbohydrate polymer, can be found in grains like
wheat, corn and oats.
Purpose:
What affect will the saliva enzyme, amylase, have on the molecules found in a cracker?
Materials and Methods:
A. Amylase enzyme-preparing the saliva
1.
Read pages 273-274 “Background Information” in your text book for test procedures
2.
Test saliva in a test tube with Benedict’s and iodine to be sure that it is free of both sugar and starch.
Continue until a lab partner has a clean saliva sample.
3.
Start with clean test tubes and label them A, B, C, D and E.
4.
Set up a data table to record the test tube letter, contents of the test tube, and the results of the sugar and
starch tests.
B. Test cracker for sugar and starch before adding the amylase enzyme.
1. Place about 1 mL of crumbled cracker in the first two test tubes (A and B) and add water up to about 2mL.
2.
Test the cracker in A for sugar with Benedict’s and a water bath. Record your results.
3.
Test the cracker in B for starch with iodine. Record your results.
4.
Spit about 1 mL of plain saliva in test tube E and put in a water bath.
C. Test cracker for sugar and starch after amylase enzyme
1. Place a cracker in your mouth and chew for 1 minute without swallowing. Spit half of the cracker in test
tube C and half in D.
2.
Test the cracker-saliva in C for sugar with Benedict’s and a water bath. Record your results.
3.
Test the cracker-saliva in D for starch with iodine. Record your results.
4.
Remove test tube E from the water bath, place some un-chewed cracker in it and test for sugar. Record
your results.
5.
Wash all test tubes and return all materials to the lab tray.
Cracker Lab-Academic (Attach lab to journal page and respond to questions in your journal)
Follow-up Questions:
1.
2.
3.
4.
5.
6.
What was the purpose of testing your saliva for sugars/starches?
What group of organic polymers does starch belong to?
What is the relationship between starch and sugar?
Why was there sugar in the cracker with enzyme (C)? Where did the sugar come from?
Why wasn’t there sugar with the cracker and HEATED enzyme (E)? What happened to the enzyme/ why?
How does the shape of an enzyme affect how it functions?