Student Exploration: Identifying Nutrients
Vocabulary: carbohydrate, disaccharide, lipid, monosaccharide, polysaccharide, protein, starch
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
1. What are the major types of nutrients you can get from food? Proteins, lipids, carbohydrates, minerals and vitamins
2. How are these nutrients used by your body?
Nutrients are used by your body for everyday functions.
Have you ever wondered what is in your food? Scientists use a variety of tests to determine the nutritional content of food. You will learn four of those tests with the Identifying Nutrients Gizmo™.
1. Below the Food samples label, drag tube A into the Food sample holder. Below the Benedict test, click the Test button. What is done in the Benedict test? The liquid turns pink when heated for 5 minutes.
2. The Benedict test is a test for monosaccharides; simple Sugars like glucose or fructose (fruit sugar). In contact with Monosaccharides, the Benedict solution turns from blue to
Does Sample A contain monosaccharides?
Note: Disaccharides such as sucrose (table sugar) and lactose (milk sugar) are more complex than monosaccharides. The Benedict test does not detect disaccharides directly.
Activity A: Identifying nutrients
| Get the Gizmo ready: *
Click Reset. *
Drag Sample A into the Food sample holder.
Introduction: Most food is composed of three types of molecules: carbohydrates, proteins, and lipids. * Carbohydrates such as starches and sugars are major source of energy. Simple sugars are found in sweets and fruits. Starches are found in potatoes, cereal, pasta, flour, and other plant products. * Proteins are used in body structures such as muscles, skin, and hair. Rich sources of proteins include meats, dairy products, and beans. * Lipids (fats and oils) are used for energy, insulation, and as an essential building block of cells. Meats, dairy products, and oily plants such as olives are rich in lipids.
Question: How do you test for carbohydrates, proteins, and lipids?
Test: Under the Benedict test, click Test. Does sample A contain monosaccharides? Yes (Recall that a pink color is a positive test for monosaccharides.)
Test: The Lugol test uses iodine to test for starch, a polysaccharide (complex sugar). Iodine turns dark purple in the presence of starch.
Under Lugol test, click Test. Does sample A contain starch? No
Test: The Biuret test uses a solution of potassium hydroxide (KOH) and copper sulfate (CuSO4) to test for protein. The Biuret solution turns purple when proteins are present.
Under Biuret test, click Test. Does sample A contain proteins? No
Test: The Sudan Red test uses a fat-soluble dye, Sudan Red, to indicate the presence of lipids. When lipids are present, the dye will be absorbed into the lipids, and will appear as concentrated spots of color in the test tube. (No spots indicates that lipids are not present.)
Under Sudan Red test, click Test. Does sample A contain lipids? No
Summarize: What nutrients does sample A contain? Polysaccharide
Analyze: What kind of food is sample A most likely to be? (Circle your choice)
A. Apple juice
B. Baked beans
D. Scrambled eggs
Activity B: Nutrients and food types
| Get the Gizmo ready: *
Question: What nutrients does each food sample contain?
1. Collect data: Use the four available tests to find the nutritional content of samples E, G, and M. (Sample A has been done for you as an example.) Record results on the table below.
| Carbohydrate Tests
| Protein Test
| Lipids Test
| Test results – are these nutrients present?
| Food sample
| Benedict test
| Lugol test
| Biuret test
| Sudan Red test
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