Interpreting Biuret and Benedict's Test Results

Steps:

• Biuret test produces purple color with proteins due to peptide bond reaction.
• Benedict's test remains blue without reducing sugars like glucose, indicating absence.
• Purple Biuret result confirms protein presence in solution.
• Blue Benedict's result confirms no glucose in solution.

Why A is correct:

• Biuret test turns purple specifically for proteins (via copper ion coordination with peptide bonds), while Benedict's stays blue without reducing sugars like glucose (no reduction of Cu²⁺ to Cu₂O).

Why the others are wrong:

• B: Incomplete and ignores Benedict's negative result for glucose, but assumes protein only partially.
• C: Contradicts Biuret's positive protein result and misinterprets Benedict's as positive for glucose.
• D: Ignores Biuret's clear positive indication of protein.

Final answer: A