A student tests four unknown solutions (A, B, C, D) for the presence of biological macromolecules using four indicators: Benedict's (reducing sugars - color change to red/orange when boiled), iodine (starch - black-blue), biuret (protein - violet), and Sudan IV (lipid - red). Results: A turns red with Benedict's; B turns blue-black with iodine; C turns violet with biuret; D turns red with Sudan IV.
Which solution most likely contains glucose?
- A
C
- B
D
- C
B
- Dcheck_circle
A
Explanation
Benedict's reagent detects reducing sugars (free aldehyde or ketone groups). Glucose is a reducing sugar; the red precipitate from Benedict's is a positive test. A is the glucose solution.