Question

Which one of the test, is not given by proteins?

• A. Biuret reaction \
• B. Benedict's test \
• C. Bicinchoninic acid (BCA) test \
• D. Folin-ciocalteu's test

Hint:

Benedict's test is exclusively for reducing sugars (like glucose). If you see sugar analysis, think Benedict's; if you see protein analysis, think Biuret, BCA, or Lowry.

Answer 1

The Correct Option is B

Step 1: Concept Analytical colorimetric tests use highly specific chemical properties of functional groups to identify or quantify classes of biomolecules such as proteins or carbohydrates.

Step 2: Meaning * Protein assays exploit peptide bonds or specific side chains (like tyrosine and tryptophan tryptophan residues). * Sugar tests detect reducing functional groups such as free aldehydes or ketones.

Step 3: Analysis * Biuret reaction (A): Specifically detects peptide bonds when copper ions coordinate with peptide nitrogens in an alkaline medium. * Benedict's test (B): Uses alkaline copper sulfate to check for the presence of reducing sugars (carbohydrates) via red cuprous oxide precipitation. It does not react with proteins. * Bicinchoninic acid (BCA) test (C): A highly sensitive assay that uses bicinchoninic acid to measure copper reduction mediated by proteins. * Folin-ciocalteu's test (D): Detects aromatic amino acid residues (tyrosine/tryptophan) via phosphomolybdate-phosphotungstate reduction.

Step 4: Conclusion Thus, Benedict's test is uniquely a carbohydrate test and is not given by proteins. Final Answer: (B)