17 Digestion - Student.pdf - haspi

Name: __________________________________________ Date: ___________ Period: _________
Materials
Spot plate 2% Albumin (protein) 1% Hydrochloric acid
20 pH strips 3% Pepsin Biuret
10 stirring sticks 1% Starch solution 2% Amylase
Forceps Potassium iodine Corn oil
Paper towels Water Liquid soap
Procedure
Purpose: The goal of this lab will be to observe how digestive enzymes are able to break down
macromolecules. All data tables are located in the analysis portion of the lab.
PART A: Protein Digestion
In part A the albumin represents a polypeptide protein. Pepsin is the enzyme needed to break down
the albumin into amino acids, but can only work within a certain pH range. The Biuret will turn pink
with smaller protein chains and will turn purple in the presence of large proteins.
1. Using a pencil, label the wells on your spot plate 1-5.
2. Place 5 drops of 2% Albumin in wells 1-4.
3. Add 5 drops of 1% HCl to wellS 2, 4, and 5.
4. Add 5 drops of 3% Pepsin to wells 3 and 4.
5. Use separate stirring sticks to mix each well, and allow them to sit for 5-7 minutes.
6. Use the forceps to dip a separate pH strip into each of the wells 1-5. Compare the color
change of each strip to the pH strip chart to determine the pH of the mixture in each well.
Record your results in Data Table 1.
7. Add 2 drops of Biuret to wells 1-5. A positive test for protein breakdown will turn pink. If the
well is positive, put a + in Data Table 1. If the well is negative put a -.
8. Record your observations of each of the mixtures in Data Table 1.
9. Rinse out your spot plate and dry it off with a paper towel.
PART B: Carbohydrate Digestion
In part B starch is a polysaccharide, and amylase is the enzyme responsible for breaking starch down
into monosaccharides. Since the potassium iodine tests for starch, you will be looking for a negative
test to determine whether amylase actually broke down the starch.
1. Using a pencil, label wells 1 and 2 on the spot plate.
2. Add 15 drops of 1% Starch solution to wells 1 and 2.
3. Add 5 drops of 2% Amylase solution to well 2.
4. Use separate stirring sticks to mix each well, and allow them to sit for 5-7 minutes.
5. Add 1 drop of Potassium iodine to wells 1 and 2. A positive test for starch will turn dark blueblack.
If a well is positive for starch, put a + in the Data Table 2. If the test is negative for
starch put a –.
6. Record your observations of each of the mixtures in Data Table 2.
7. Rinse out your spot plate and dry it off with a paper towel.
Adapted from Neo/Sci Food Digestion Lab Activity 2011 237