INSTRUCTION SHEET- RETURN AT END OF PERIOD
Honors Biology
Testing Foods for Organic Compounds Lab
Introduction
Carbohydrates, proteins, and lipids provide your body with energy to carry on life activities. These compounds are present in the plants and animals you use as food. In this lab, you will test for specific biological compounds and then determine if those compounds are present in ordinary foods. To do this you will use indicators to test for three organic compounds.
Indicators are dyes which change color in the presence of certain organic compounds.
· Benedict’s solution turns from blue to orange in the presence of glucose.
· Iodine turns from amber to bluish black in the presence of starch.
· Biuret solution turns from blue to lilac (light purple) in the presence of protein.
· Sudan IV will change the color of a fat to red in the presence of lipids.
Purpose: determine the presence of organic molecules in common foods.
Procedure:
1. Go to pdecandia.com. Select the Biology or Scholars Biology page. Click on the Organic Chemistry
picture link. Click on the link in the lab section for “Testing Foods for Organic Compounds”.
2. Click on each of the links in order and follow the directions in each section.
3. When you are done with the carbohydrate section, go on to the proteins, then the fats section and
complete each part of the lab. Record your answers for each exercise in the data sheet.
4. Once you are finished with the organic compounds tests, move on to the foods section of the lab and record
your results for each of the foods in the data table.
Name ______
Honors Biology
Testing Foods for Organic Compounds Lab Data Sheet
1. When we test water, what should the result always be? What is the purpose of testing water for each organic
molecule?
2. What does an indicator do?
Simple Sugar Test
1. What organic molecule does Benedicts reagent test for?
2. What color is a negative result? A positive result?
Carbohydrates Section
1. What organic molecule does iodine test for?
2. What color is a negative result? A positive result?
3. People with diabetes are instructed to avoid foods that are rich in carbohydrates. What types of foods should
people with diabetes avoid?
Proteins Section
1. What organic molecule does Biuret reagent test for?
2. What color is a negative result? A positive result?
3. List five foods that contain proteins.
Lipids Section
1. What organic molecule does Sudan IV reagent test for?
2. What color is a negative result? A positive result?
3. List five foods that contain lipids.
Food Section Data Table
Record as follows: + positive result - negative result
+ / -
(glucose) / Iodine test
+ / -
(starch) / Biuret test
+ / -
(protein) / Sudan test
+/ -
(lipid)
Potatoes
Orange juice
Nuts
Eggs
Salmon
Milk
Post Lab Practice Evaluation
Determine the organic molecule/molecules in the above unknown samples and fill in the name of the molecule with the coordinating number on the blank lines below the chart.
Unknown food sample / Benedict’s / Iodine / Biuret / SudanIV
1 / Orange / Amber / Blue / -
2 / Blue / Blue/black / Purple / -
3 / Blue / Blue/black / Blue / +
4 / Orange / Amber / Blue / +
5 / Blue / Blue/black / Blue / -
Unknown food sample organic compounds found in this sample
1 ______
2 ______
3 ______
4 ______
5 ______
Identify the following:
independent variable: / Constants:
dependent variable:
Post Lab Analysis
1. Which food sample/samples would be insoluble in water?
2. Water alone, would not remove a stain from clothing that was made by yours(s) in the above question. What
would interact with the fats to break them into smaller globules and be removed?
3. What is the general rule of solubility of substances?
4. You are a dietician and have to recommend a balanced food plan for a customer. Using your knowledge of
the organic molecules contained in food from this lab, write out a three meal menu with foods for each meal
that contain the three organic molecules, proteins, carbohydrate, and lipids. Be sure to write the meal, each
food and list the organic compounds found in each food.
DO NOT REPEAT SAME FOODS IN ANY MEAL
1.
2.
3. / Organic Molecule/molecules in each food
1.
2.
3.
Lunch / Food
1.
2.
3. / Organic Molecule/molecules in each food
1.
2.
3.
Dinner / Food
1.
2.
3. / Organic Molecule/molecules in each food
1.
2.
3.
Conclusion:
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