identifying macromolecules in food lab adapted from: madison southern high school biology
TRANSCRIPT
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IDENTIFYING MACROMOLECULES
IN FOODLAB
Adapted from:
Madison Southern High School
Biology
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Introduction
Carbohydrates, proteins, and fats are all essential nutrients.
We cannot manufacture these nutrients so we must obtain them from our environment.
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Introduction
In this lab, with the use of indicators as chemical detection tools, you will analyze a variety of foods for the presence of nutrients.
Detection is based upon observing a chemical change that takes place most often a change in color.
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Objective
Identify the presence of major nutrients such as simple carbohydrates (glucose),
complex carbohydrates (starch), protein and fat in common foods.
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What is an indicator?
• Indicators are chemical compounds used to detect the presence of other compounds.
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Background Information
INDICATOR MACRO-MOLECULE
NEGATIVE TEST
POSITIVE TEST
Benedict’s solution
simple carbohydrate
blue orange
IKI solution complex carbohydrate
dark red black
Biuret solution
protein blue violet, black
Sudan IV lipid dark red reddish- orange
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What is a Standard?
• An acknowledged measure of comparison for quantitative or qualitative value; a criterion.
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Test for Simple CarbohydratesBenedict’s solution
• Benedict's solution is a chemical indicator for simple sugars such as glucose: C6H12O6.
• Aqua blue: negative test; yellow/green/brick red, etc.: positive test
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Test for Simple CarbohydratesBenedict’s solution
• Unlike some other indicators, Benedict’s solution does not work at room temperature - it must be heated first.
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Test for Complex CarbohydratesIKI solution
• IKI solution (Iodine Potassium Iodine) color change = blue to black
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Test for Complex CarbohydratesIKI solution
• Iodine solution is an indicator for a molecule called starch.
• Starch is a huge molecule made up of hundreds of simple sugar molecules (such as glucose) connected to each other.
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Test for Protein (amino acids)Biuret solution
• Biuret solution dark violet blue to pinkish purple
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Test for Fats (lipids)Sudan IV
• Like lipids, the chemical Sudan IV is not soluble in water; it is, however, soluble in lipids.
• In this test dark red Sudan IV is added to a solution along with ethanol to dissolve any possible lipids.
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Test for Fats (lipids)Sudan IV
• If lipids are present the Sudan IV will stain them reddish-orange (positive test).
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QuestionWhy didn’t the test tube containing sucrose
change colors?
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Question
Why didn’t the test tube containing starch change colors?
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ProcedureSimple carbohydrate
1. Add 5ml distilled H2O
using pipette to test tube
2. Add 3ml of food sample to test tube
3. Add 10-20 drops of Benedict solution
4. Place test tube in a hot water bath for 10 minutes.
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ProcedureComplex carbohydrate
1. Add 5ml distilled H2O using pipette
to test tube
2. Add 3ml of food sample to test tube
3. Add 10-20 drops of IKI solution
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ProcedureProtein (amino acids)
1. Add 5ml distilled H2O using pipette
to test tube
2. Add 3ml of food sample to test tube
3. Add 10-20 drops of Biuret solution
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ProcedureFats (lipids)
• Add 5ml distilled H2O using pipette to test tube
• Add 3ml of food sample to test tube
• Add 10-20 drops of Sudan IV
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LAB SAFETY and CLEAN UP
WEAR safety goggles and
apron at all times
THOROUGHLY CLEAN lab area and equipment
NO EDIBLE products
in lab
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• Your first Experimental Design Project: due November 12th.
– Research a laboratory experiment that has been conducted and communicates its results.
– Using the Experimental Design Reference, write the Lab report using the guidelines and categories as indicated on the Experimental Design Reference.