B. IODINE TEST FOR STARCHES 1. What was the purpose of water in this experiment? 2. Which gave a stronger positive result (more intense color), apple juice or potato juice? 3. Is starch ever present in animal products such as milk, meat or eggs? Explain. 4. Why did the glucose solutions give a negative result? C. SUDAN TEST FOR LIPID 1. Do you think the milk was whole milk or skim milk? Why? 2. Where were the Sudan crystals found in the well containing water? D. BIURET TEST FOR PROTEIN 1. Do free amino acids have peptide bonds? Explain why or why not. 2. Which solutions had a strong positive result? Were any of these surprising to you? R INSTRUCTOR: A. BENEDICT'S TEST FOR REDUCING SUGARS Test tube distilled water 0.05% glucose 1% glucose 5% flour solution apple juice potato juice milk Spot B. IODINE TEST FOR STARCHES distilled water 0.05% glucose 1% glucose 5% flour solution apple juice potato juice milk Color orange Green Yellow light Blue blight Red and dark blue Red/orange Green Bive Color SECTION/GROUP: Amber Amber Amber Purple DATA: LABORATORY 3 Amber Green & Pieces Amber Positive or Negative? Negative Positive Positive Positive Positive Positive Positive Positive or Negative? Negative Negative Negative positive Negative positive Negative Laboratory 3 Macromolecules. 25 C. SUDAN TEST FOR LIPID Substance Tested water cream milk vegetable oil 5% flour solution D. BIURET TEST FOR PROTEIN Test tube milk distilled water egg albumin starch solution chicken broth apple juice gelatin Dissolved? (Yes/No) No Yes yes yes NO Color Blue Porple light Blue Purple Purple Yellow Purple Positive or Negative? Negative Positive Positive Positive Negative Positive or Negative? Negative Positive Negative Positive Positive Negative Positive DO-IT-YOURSELF BIOLOGY TESTING AN UNKNOWN You will perform four tests on each of the unknowns. Record your results in the following table. Based on the results, you will suggest their identity: reducing sugars, starch, lipid, or protein. The unknowns are labeled A, B, C and D. Before you test each unknown, develop your hypotheses regarding what results you expect to get for each of the four possible substances. E. CHEMICAL TESTING TO IDENTIFY AN UNKNOWN Benedict's Test lodine Test Sudan Test Unknown A B D Neg Pos Neg Meg she g Pos Neg Neg Neg Neg Pos Biuret Test Pos Neg Unknown Identity protien Sugar Starch deg Neg lipid