lab identifying macromolecules in food july 31 2012 1

Topics: Protein, Urinalysis, Glucose Pages: 39 (3277 words) Published: March 11, 2015
Teacher’s Guide
EXPLORE
Part I: Testing Known Substances

Teacher Prep:
1. Prepare and label four Erlenmeyer flasks and disposable pipettes with the following suggested solutions and place them in the front of the room for easy access for students: a. Polysaccharide Solution - blended potato or lab grade starch solution b. Monosaccharide Solution – apple juice or lab grade glucose solution c. Protein Solution – blended meat or egg whites

d. Lipid Solution – vegetable oil, melted butter
2. Set up 4 lab stations (twice around the room) for students to rotate. Each station should have the materials needed to conduct one of the following tests: a. Iodine Test: starch + iodine (yellowish orange)  blue-black Ex. Potato solution

b. Benedict's Test: monosaccharide + Benedict's solution (light blue)  green to red depending on concentration of sugars Ex. apple juice or glucose solution
c. Biuret's Test: protein solution + Biuret’s solution (light blue)  pinkish purple
Ex. meat , egg white
d. Paper Bag (Translucence) test
3. At each station, have the indicator test procedure card, the biomolecule information card for the biomolecule being tested at the station, and all lab supplies required to conduct the test. It is recommended that the two lab stations in the front be designated for the Benedicts test which requires a hot water bath. Procedure

4. Have students read the background information and complete the Pre-Lab questions for Part 1 as the journal activity for the day. 5. Demonstrate to students what equipment and basic procedures they will be applying during this exercise. 6. Have students get into groups of 2-3 and rotate through all 4 stations and record their results. 7. Have students return to their desks but stay with their groups to complete the Analysis Questions in their journals.

Alternate indicators:
Iodine for lipids/oil (turns pink but transformation is temporary so watch carefully) Biuret Solution is easy to make. Start with 40% NaOH and then sprinkle in copper sulfate until you get a nice blue color. Nitric acid for proteins (turns yellow in the presence of proteins, stays clear if none are present). Students need to take the proper cautions when working with nitric acid to prevent contact with skin or clothing.  It becomes really easy to see who did not take proper precautions because they can be caught yellow-handed. Water solubility test for fats (the presence of fats makes an insoluble layer on top of the water).  This test can be difficult at times to detect based on the type of substance and amount of fat in it.

ELABORATE
Part II: A Lesson in Urinalysis

Teacher Prep:
1. Prepare and label four Erlenmeyer flasks and disposable pipettes with the following synthetic urine solutions and place them in the front of the room for easy access for students: Synthetic Urine Recipes

Each student group needs about 10 mL of a sample for testing. These recipes make about 60 mL of each sample.

Stock Urine:
160mL water
Yellow food coloring
2g NaCl

Urine Sample from Patient #H 987
(High glucose)
40mL apple juice
20mL stock urine

Urine Sample from Patient #L 623
(High protein)
60mL stock urine
5mL egg albumin

Urine Sample from Patient #P 552
(High glucose & protein)
40mL apple juice
20mL stock urine
5mL egg albumin

Urine Sample from Patient #M 340
(High protein & High starch – contaminated sample!)
50mL stock urine
5mL egg albumin
5mL starch

2. Set up 3 lab stations (2-3 times around the room) for students to rotate. Each station should have the materials needed to conduct one of the following tests: a. Iodine Test: starch + iodine (yellowish orange)  blue-black Ex. Potato solution

b. Benedict's Test: monosaccharide + Benedict's solution (light blue)  green to red depending on concentration of sugars Ex. apple juice or glucose solution
c. Biuret's Test: protein solution + Biuret’s solution (light blue)  pinkish purple
Ex. meat , egg...
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