Questions for Reasearch:1. According to the results of each part of the experiment, identify your unknown and explain your reasoning.2. Compare the results you obtained for the iodine test of starch to the iodine test of hydrolyzed starch. Explain your results.3. What is meant by the term "reducing sugar"?4. Draw the ring structures for a-D-fructose and for B-D-fructose.5. What test could be used to differentiate between sucrose and lactose?Explain.6. What test could be used to differentiate between glucose and starch? Explain.7. What test could be used to differentiate between glucose and fructose? Explain.8. Why don't all of the disaccharides undergo fermentation with yeast?
Answer (1)
Hydrolysis breaks starch into smaller sugars (maltose or glucose) that don’t form the starch-iodine complex.3. Reducing sugar:A sugar that can donate electrons to another molecule, usually detected by Benedict’s or Fehling’s test.Examples: glucose, fructose, maltose.4. Ring structures of fructose:Draw α-D-fructose and β-D-fructose as five-membered furanose rings.The difference is in the orientation of the OH group on the anomeric carbon: down for α, up for β.5. Test to differentiate sucrose and lactose:Benedict’s test:Lactose = reducing sugar → gives a positive Benedict’s test (red/orange precipitate)Sucrose = non-reducing sugar → gives a negative Benedict’s test unless hydrolyzed first.6. Test to differentiate glucose and starch:Iodine test:Starch → blue-black (positive).Glucose → no color change.
