Podcast
Questions and Answers
Which amino acid specifically requires sulfuric acid as a catalyst in the Xanthoproteic Test?
Which amino acid specifically requires sulfuric acid as a catalyst in the Xanthoproteic Test?
Which amino acid is tested specifically by the Hopkins-Cole Test?
Which amino acid is tested specifically by the Hopkins-Cole Test?
What color indicates a positive result for the Sakaguchi Test when arginine is present?
What color indicates a positive result for the Sakaguchi Test when arginine is present?
In the Bromine Water Test, which amino acid undergoes halogenation resulting in a pink/lavender color?
In the Bromine Water Test, which amino acid undergoes halogenation resulting in a pink/lavender color?
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What is the result of the Unoxidized Sulfur Test for sulfur-containing amino acids like cysteine?
What is the result of the Unoxidized Sulfur Test for sulfur-containing amino acids like cysteine?
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What color indicates a positive result in the Biuret test for proteins?
What color indicates a positive result in the Biuret test for proteins?
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Which amino acid is specifically tested with the Millon-Nasse test?
Which amino acid is specifically tested with the Millon-Nasse test?
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What is the main component of the reagent used in the Ninhydrin test?
What is the main component of the reagent used in the Ninhydrin test?
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What type of solution results from the reaction of aromatic rings with Xanthoprot?
What type of solution results from the reaction of aromatic rings with Xanthoprot?
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In a positive Millon's test, what color does the complex turn upon heating?
In a positive Millon's test, what color does the complex turn upon heating?
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What is a characteristic color change observed in a positive Ninhydrin test?
What is a characteristic color change observed in a positive Ninhydrin test?
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What is the outcome of the reaction between unoxidized NaOH and sulfur in the presence of cysteine?
What is the outcome of the reaction between unoxidized NaOH and sulfur in the presence of cysteine?
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What does the intensity of the violet color in the Biuret test indicate?
What does the intensity of the violet color in the Biuret test indicate?
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Study Notes
Color Reactions of Amino Acids and Proteins
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Biuret Test
- Composed of 10% NaOH and 0.01M CuSO₄.
- Positive result yields a violet solution, indicating the presence of peptide bonds.
- Commonly tests for albumin or any peptide.
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Ninhydrin Test
- Utilizes ninhydrin solution.
- Produces a dark blue/violet solution, indicating amines or free amino acids.
- Confirmed positive with albumin and various proteins.
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Xanthoproteic Test
- Conducted with concentrated HNO₃ and sodium hydroxide.
- Positive result is a yellow solution, indicative of proteins containing aromatic amino acids (tyrosine, tryptophan).
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Millon's Test
- Uses Millon’s reagent, a mixture of mercuric and mercurous nitrates.
- Positive result shows initial white precipitate, turning brick-red upon heating.
- Specific for proteins yielding tyrosine on hydrolysis due to the phenolic group.
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Thiol Group Test (Cysteine)
- Involves unoxidized 10% NaOH, producing a black precipitate with lead acetate.
- Presence of thiol groups in cysteine leads to black lead sulfide formation.
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Hopkins-Cole Test
- Specific to tryptophan containing an indole group.
- Positive result yields a violet cyclic product when reacted with glyoxylic acid in strong acid conditions.
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Sakaguchi Test
- Detects arginine.
- The sample treated with alpha-naphthol and sodium hypochlorite yields a reddish wine color upon a positive test.
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Bromine Water Test
- Tests pyrrole ring in tryptophan through halogenation.
- Positive result leads to a pink/lavender color.
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Unoxidized Sulfur Test
- Targets sulfur-containing amino acids, specifically cysteine.
- Liberated sulfur reacts with lead acetate to yield a black precipitate of lead sulfide.
General Notes on Protein Testing
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Biuret Test Significance
- Indicates presence of peptide bonds following hydrolysis and is color-intensity correlated with peptide bond quantity.
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Ninhydrin Specifics
- Used broadly for detecting proteins by producing a distinct color change.
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Phenolic Group Reactions
- Millon's and Xanthoproteic tests exploit the unique nature of phenolic compounds in specific amino acids.
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Aromatic Amino Acid Identification
- Xanthoproteic test highlights aromatic amino acids, crucial in understanding protein structure.
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Indole Group Specificity
- Hopkins-Cole uniquely identifies tryptophan due to its indole presence, critical for metabolic studies.
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Sakaguchi Test Utility
- Often employed in research and diagnostic scenarios to confirm arginine presence.
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Description
Explore the color reactions of various amino acids and proteins through different tests. This quiz covers essential reactions such as Biuret, Ninhydrin, and Xanthoproteic tests, detailing the reagents used and the expected results. Test your understanding of these biochemical assays and their significance.
