Carbohydrate/ Enzyme Labs
Name ____________
http://eve.kean.edu/~breid/enzyme/enzyme.html
This is a very complete and well designed website with tutorials, animations and
complete explanations. Check it for fun or for help.
Enzymes are proteins that metabolize a specific substance.
As an enzyme works, it combines with its substrate and converts it to product(s). The enzyme can do
this as long as there is substrate available or unless it is denatured. You can monitor the activity of the
enzymes by observing changes in the amounts of substrate and/or products.
Today we will focus on Amylase, an enzyme that catalyzes the hydrolysis of polysaccharides.
SUBSTRATE
ENZYME
- - - - - >
PRODUCTS
Benedict's Test for Reducing Sugars. The sugar test is performed by adding a small amount of
Benedict's Reagent to the sample and heating the mixture. If the Benedict's Reagent retains its blue
color and no precipitate is formed, sugar is absent. The presence of sugar is indicated by the
development of a precipitate which may range in color (indicating increasing amounts of sugar) from
green, through yellow and orange, to red. This test depends upon the ability of certain sugars to
reduce the cupric (Cu++) copper (blue) present in the Benedict's Reagent to the cuprous (Cu+) form
(red).
0
*Blue
None
+
Green
Some
++
Yellow
More
+++
Orange
Much
Red
Most
. . . . . . . ++++
Color Symbol Description Amount of Amylase Activity
* blue = 0 (no precipitate; no color change)
Materials:
9 (or 10) Test tubes
Benedict’s solution
Starch suspension
Saliva from a willing volunteer, about 10 mL
Maltose, glucose, waxed paper, spatulas
Water bath (beaker, hot plate, tap water)
Test tube rack
Oatmeal, mortar and pestle
Procedure:
1. Using the sharpie, number the test tubes 1-9 (or 10).
2. Oatmeal suspension: Grind about a ¼ teaspoonful of oatmeal in a mortar and
pestle. Pour the ground oatmeal into a small beaker with about 10 mL water. Or
the willing volunteer can chew the oatmeal to fine consistency for tubes 4 and 7.
3. Your test tubes should contain:
1. Benedict’s solution, 1ml (about 20 drops);
2. Benedict’s, 1ml + glucose (an amount the size of a lentil)
3. Benedict’s, 1ml + oatmeal suspension, 1ml
4. Benedict’s, 1ml + oatmeal suspension, 1ml + saliva
5. oatmeal suspension, 1 ml
6. Lugol’s solution, 1ml + oatmeal suspension, 1ml.
7. Lugol’s solution, 1ml + oatmeal suspension, 1ml. + saliva
8. Lugol’s solution, 1ml and saliva
9. Benedict’s solution, 1ml and saliva
10. Optional: Paper towel + saliva + Benedict’s , 1ml
4. (5) Prepare a data table by drawing the 9 (or 10) test tubes and labeling the
contents.
5. Start water bath for heating Benedict’s test; after heating for about 5 minutes,
remove the test tubes carefully, return to the rack, and turn off the heat.
6. Record your results above by drawing the color changes after heating the tubes.
7. Clean all test tubes thoroughly by scrubbing with a test tube brush, rinsing and
leaving them draining upside down in your test tube rack on a paper towel AT
YOUR TABLE. Clean the mortar and pestle and leave in the dish drainer. If the
water bath is cool enough to handle, pour out the hot water in your sink and place
the beaker upside down on a paper towel at your table.
8. (10) Answer questions on this sheet; cite sources at the end:
a. In which test tubes was a reducing sugar detected?
b. If you detected reducing sugars in ground oatmeal, explain why oats might
contain some, or might not.
c. If you detected reducing sugars in ground oatmeal + saliva, explain why
that might be the case.
d. Oatmeal comes from a particular plant part that is usually quite high in
starch. What plant part? ___________________________What category of
plants are oats a part of? (Hint: part of the name of this plant category is a
word often used to complete this phrase: breakfast __________________,
and most societies around the world eat one or more of these crops).
e. Explain any differences between test tubes #6 and #7.
f. In which test tubes is there evidence of digestion by amylase? Explain.
g. What is amylase’s substrate, and what is its product?
h. What is the effect on the enzyme/substrate process of grinding or chewing
the food before swallowing it?
i. Of what value is it to the human being to be able to digest starch?
j. Sources:
9. (5) Draw (please don’t just print them out!) ring-structure glucose, fructose and
sucrose molecules showing all atoms. Find a three-dimensional drawing as your
model, such as on:
http://cdavies.wordpress.com/2009/01/27/simple-sugars-fructose-glucose-and-sucrose/
Honors: look carefully at sucrose and tell what small molecule was “lost” when the two
monosaccharides combined to form the disaccharide: ____________