Sugars

• What are the building blocks of larger carbohydrates?

  Monosaccharides
• How is a disaccharide formed?

  By joining two monosaccharides together
• What type of reaction joins monosaccharides?

  Condensation reactions
• What bond forms between two monosaccharides?

  Glycosidic bond
• What is formed when two α-glucose molecules join?

  Maltose
• What is sucrose made from?

  Glucose and fructose
• What two monosaccharides form lactose?

  Glucose and galactose
• What are the learning objectives regarding monosaccharides and disaccharides?

  • Monosaccharides are monomers for carbohydrates
  • Glucose and fructose are hexoses in ring and chain forms
  • Glucose and galactose are isomers differing in arrangement
  • Disaccharides form from condensation of monosaccharides
  • Maltose is from two glucose molecules
  • Sucrose is from glucose and fructose
  • Lactose is from glucose and galactose
• How are sugars classified?

  As reducing or non-reducing sugars
• What does the Benedict's test detect?

  Reducing sugars
• What happens when Benedict's reagent is added to a reducing sugar?

  It forms a colored precipitate
• What indicates a positive result in the Benedict's test?

  Colored precipitate forms
• What must be done to test for non-reducing sugars?

  Break them down into monosaccharides
• What is the first step in testing for non-reducing sugars?

  Add dilute hydrochloric acid
• How do you neutralize the solution after adding hydrochloric acid?

  By adding sodium hydrogencarbonate
• What are the steps to perform the Benedict's test for non-reducing sugars?

  1. Add dilute hydrochloric acid to the sample
  2. Heat in a boiling water bath
  3. Neutralize with sodium hydrogencarbonate
  4. Perform the Benedict's test as for reducing sugars
• What is the significance of the color change in the Benedict's test?

  Indicates concentration of reducing sugar
• How does the concentration of reducing sugar affect the Benedict's test result?

  Higher concentration leads to greater color change
• What is the purpose of filtering the solution in the Benedict's test?

  To weigh the precipitate accurately
• What is a colorimeter used for in the Benedict's test?

  To measure absorbance of remaining reagent