Carbohydrates

• What is the result of a positive iodine test for starch?

  The solution changes to blue-black.
• What is the structural difference between amylose and amylopectin?

  Amylose is unbranched; amylopectin is branched.
• Why is glycogen more efficient for energy storage in animals?

  It is highly branched for faster glucose release.
• What color change occurs in Benedict’s test if reducing sugars are present?

  The solution changes from blue to brick red.
• What steps are needed to test for non-reducing sugars?

  1. Perform Benedict’s test (no change = no reducing sugars)
  2. Add HCl and heat to hydrolyze
  3. Neutralize with sodium hydrogen carbonate
  4. Repeat Benedict’s test
  5. If precipitate forms, non-reducing sugars are present.
• What is the role of cellulose in plants?

  It provides structural support to cell walls.
• Why don't starch and glycogen affect water potential?

  Because they are insoluble in water.
• What color in the Benedict’s test indicates a high sugar concentration?

  Brick red.