IDENTIFYING MACROMOLECULES IN FOOD LAB

Introduction Carbohydrates, proteins, and fats are all essential nutrients. We cannot manufacture these nutrients, so we must obtain them from our environment. The presence of these macromolecules can be detected by chemical indicators

Introduction In 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.

Objective Identify the presence of major nutrients such as simple carbohydrates (glucose), complex carbohydrates (starch), protein and fat in common foods.

What is an indicator? Indicators are chemical compounds used to detect the presence of other compounds.

Background Information INDICATOR MACRO-MOLECULE NEGATIVE TEST POSITIVE TEST Benedict’s solution simple carbohydrate blue orange Lugol’s solution complex carbohydrate dark red black Biuret solution protein violet, black Sudan III lipid reddish- orange

Test for Simple Carbohydrates Benedict’s solution Benedict's solution is a chemical indicator for simple sugars such as glucose: C6H12O6.  yellow/green/brick red, etc.: positive test

Test for Simple Carbohydrates Benedict’s solution Unlike some other indicators, Benedict’s solution does not work at room temperature - it must be heated first.

Procedure Simple carbohydrate Add 2ml of food sample to test tube Add 8 drops of Benedict solution Place test tube in a hot water bath for 10 minutes.

Test for Complex Carbohydrates IKI solution (Lugol’s 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.

Test for Complex Carbohydrates IKI solution IKI solution  (Iodine Potassium Iodine) color change = blue to black

Procedure Complex carbohydrate Add 2ml of food sample to test tube Add 8 drops of Lugols solution

Test for Protein (amino acids) Biuret solution Biuret solution  dark violet blue to pinkish purple is positive for protein

Procedure Protein (amino acids) Add 2ml of food sample to test tube Add 8 drops of Biuret solution

Test for Fats (lipids) Sudan III Like lipids, the chemical Sudan III is not soluble in water; it is, however, soluble in lipids. In this test dark red Sudan III is added to a solution along with ethanol to dissolve any possible lipids.

Test for Fats (lipids) Sudan III If lipids are present the Sudan III will stain them reddish-orange (positive test).

Procedure Fats (lipids) Add 2ml of food sample to test tube, then 2 ml of distilled water. Add 10 drops of Sudan IV *do not shake!!

LAB SAFETY and CLEAN UP NO EDIBLE products in lab WEAR safety goggles and apron at all times THOROUGHLY CLEAN lab area and equipment

Murder and a Meal

Conclusion Report your findings in discussion format. Open the discussion with a statement regarding which restaurant the victim visited for his last meal (1 point). Provide a logical explanation, using data from the tests on the stomach contents, that explains how you reached that conclusion (4 points). The discussion should explain the results of the investigation in regard to the scientific concepts that are being applied in the investigation. In this case, the scientific concept being applied are macromolecules and the specific chemical tests used to determine their presence (5 points)

Simple Carbohydrate Complex Carbohydrate Protein (amino acids) Add 2ml of food sample to test tube Add 8 drops of Benedict solution Place test tube in a hot water bath for 10 minutes. Complex Carbohydrate Add 2ml of food sample to test tube Add 8 drops of Lugols solution Protein (amino acids) Add 2ml of food sample to test tube Add 8 drops of Biuret solution Fats (lipids) 1. Add 2ml of food sample to test tube, then 2 ml of distilled water. 2. Add 10 drops of Sudan IV *do not shake!!