Testing for carbohydrates: Benedict's and iodine tests

• What is the main difference between reducing and non-reducing sugars?

  Reducing sugars have free aldehyde or ketone groups
• What is Benedict's reagent primarily composed of?

  Copper sulfate solution
• How does the final color in the Benedict's test relate to sugar concentration?

  • Blue: no sugar
  • Green: low sugar
  • Yellow: moderate sugar
  • Brick-red: high sugar
• Which reducing sugars can be detected using the Benedict's test?

  Glucose and fructose
• What is iodine solution used for?

  To test for starch
• Why does iodine change color when it contacts starch?

  Starch molecules trap iodine, causing a color change
• What are the two options for heating the sample and Benedict's reagent mixture?

  • Water bath
  • Burner (heat for 3-5 minutes)
• What are the color changes observed with iodine solution in the presence or absence of starch?

  • Present: Blue-black
  • Absent: Brown
• What are the uses of the iodine test?

  The iodine test is used to detect the presence of starch in various samples, such as food, plant materials, and biological samples.
• What happens to copper ions in Benedict's reagent when heated with reducing sugars?

  Cu²⁺ ions are reduced to Cu⁺ ions
• How does Benedict's reagent function in testing?

  It tests based on reducing power
• Why do reducing sugars change the color of Benedict's reagent?

  They donate electrons during reduction