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Xanthoproteic Test for Aromatic Amino Acids
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Xanthoproteic Test for Aromatic Amino Acids

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@VeritableJadeite

Questions and Answers

What happens to coagulable proteins when heated at their isoelectric pH?

  • They dissolve back into the liquid.
  • They form a dense coagulum. (correct)
  • They are completely denatured and lose all structure.
  • They remain in their original structure without changes.

    • Which of the following statements is true regarding proteins and their interaction with acids?

  • All proteins coagulate equally in acidic solutions.
  • Proteins only react with strong acids to form a coagulum.
  • Heating proteins in an acidic medium can lead to their denaturation. (correct)
  • Proteins will precipitate at their isoelectric pH regardless of other conditions.

    • What role do weak bonds play in the denaturation of proteins during heating?

  • They are broken, resulting in protein unfolding. (correct)
  • They enhance the protein's solubility.
  • They stabilize the protein structure.
  • They prevent the formation of a coagulum.

    • What is the expected outcome of heating gelatin in the heat coagulation test?

    <p>No coagulation will occur.</p> Signup and view all the answers

    Why do proteins have a net zero charge at their isoelectric pH?

    <p>The amount of positive and negative charges balance out.</p> Signup and view all the answers

    What effect does heating have on polypeptides, which are non-coagulable proteins?

    <p>They remain unchanged after heating.</p> Signup and view all the answers

    What primarily determines the coagulation of proteins during the heat coagulation test?

    <p>The concentration and particle size of the proteins.</p> Signup and view all the answers

    Which type of protein is expected to show a dense coagulum during the test?

    <p>Globulins.</p> Signup and view all the answers

    What is required to precipitate proteins like albumin according to the procedure described?

    <p>Adjust the pH to the isoelectric point and then heat the solution</p> Signup and view all the answers

    What indicates the presence of protein in the xanthoproteic test?

    <p>Development of a yellow color</p> Signup and view all the answers

    During the procedure, how is the acrimony of HNO3 categorized?

    <p>As a strong oxidizing agent and corrosive substance</p> Signup and view all the answers

    What role does 1% acetic acid play in the protein precipitation process?

    <p>It brings albumin to its isoelectric point</p> Signup and view all the answers

    What should be done after adding concentrated HNO3 to the test tubes?

    <p>Cool the test tubes under tap water</p> Signup and view all the answers

    What is the expected outcome after heating the top half of the test tube in the xanthoproteic test?

    <p>Yellow precipitate formation</p> Signup and view all the answers

    Which amino acids are specifically detected through the xanthoproteic test?

    <p>Aromatic amino acids like phenylalanine, tyrosine, and tryptophan</p> Signup and view all the answers

    What is the purpose of cooling the test tubes under tap water before observation?

    <p>To allow for temperature stabilization before recording observations</p> Signup and view all the answers

    What is the primary use of the xanthoproteic test?

    <p>To detect amino acids with aromatic nuclei</p> Signup and view all the answers

    What is the expected color change when alkali is added to the nitro derivatives formed in the xanthoproteic test?

    <p>From yellow to orange</p> Signup and view all the answers

    Which chemical is primarily used to form the nitro derivatives in the xanthoproteic test?

    <p>Concentrated nitric acid (HNO3)</p> Signup and view all the answers

    What type of amino acids gives a positive result in the xanthoproteic test?

    <p>Aromatic amino acids</p> Signup and view all the answers

    What is a potential consequence of heating coagulable protein at isoelectric pH?

    <p>Irreversible breakdown of peptide bonds</p> Signup and view all the answers

    Which material is NOT listed as part of the xanthoproteic test setup?

    <p>Potassium chloride</p> Signup and view all the answers

    In preparing a 40% NaOH solution, what is the total volume of solution obtained from dissolving 40 gm of NaOH in distilled water?

    <p>100 mL</p> Signup and view all the answers

    Which of the following amino acids is identified through the xanthoproteic test?

    <p>Tryptophan</p> Signup and view all the answers

    What chemical reaction is primarily responsible for the development of a green color in Fouchet's test?

    <p>Oxidation of bilirubin to biliverdin</p> Signup and view all the answers

    Which reagent is used to precipitate sulfate radicals present in urine during Fouchet's test?

    <p>Barium chloride</p> Signup and view all the answers

    What is the significance of the green color formation in urine testing?

    <p>Presence of bilirubin due to liver dysfunction</p> Signup and view all the answers

    What role does trichloroacetic acid (TCA) play in the detection of bilirubin in urine?

    <p>It releases adsorbed bilirubin from precipitates</p> Signup and view all the answers

    In the context of the described case, what condition might the 4-day old premature infant be suffering from?

    <p>Hyperbilirubinemia</p> Signup and view all the answers

    Which component of Fouchet's reagent is responsible for the oxidation of bilirubin?

    <p>Ferric chloride</p> Signup and view all the answers

    What initial step is taken in the procedure for performing Fouchet's test?

    <p>Place 5 ml of fresh urine in a test tube</p> Signup and view all the answers

    What is the primary substance that adheres to the barium sulfate precipitate in the context of these tests?

    <p>Bilirubin</p> Signup and view all the answers

    What substance is primarily detected through Fouchet's test?

    <p>Bile pigments</p> Signup and view all the answers

    Which of the following components is NOT part of Fouchet’s reagent?

    <p>Citric acid</p> Signup and view all the answers

    What color indicates a positive result for bile pigments in Fouchet's test?

    <p>Greenish blue</p> Signup and view all the answers

    Which of the following diseases is associated with increased bilirubin in urine?

    <p>Obstructive jaundice</p> Signup and view all the answers

    In the context of Fouchet's test, how is protein affected when heated in an acidic medium?

    <p>It retains its primary structure but denatures reversible</p> Signup and view all the answers

    Which of the following can be used as an alternative to Fouchet's solution in the test?

    <p>Yellow colored HNO3</p> Signup and view all the answers

    Which abnormal constituent of urine is primarily tested for using Fouchet's test?

    <p>Bilirubin</p> Signup and view all the answers

    What role does barium chloride play in the materials listed for Fouchet's test?

    <p>It acts as a precipitating agent</p> Signup and view all the answers

    Study Notes

    Xanthoproteic Test

    • Detects aromatic amino acids: Tyrosine and Tryptophan.
    • Materials Needed: Bunsen burner, 2 test tubes, distilled water, concentrated HNO3, and 40% NaOH solution.
    • Principle: Upon heating amino acids with concentrated HNO3, yellow nitro derivatives form, indicating the presence of tyrosine and tryptophan.
    • Differentiates aromatic amino acids from non-aromatic ones based on positive results.
    • Yellow color observed confirms protein presence.

    Method for Xanthoproteic Test

    • Mix 1 mL test solution in one test tube, and add 1 mL distilled water in another.
    • Add 1 mL concentrated HNO3 to both tubes and heat for 1-2 minutes.
    • Cool and add 1 mL of 40% NaOH; observe color change: yellow indicates the presence of proteins.

    Heat Coagulation Test

    • Determines presence of proteins in a solution.
    • Materials: 1% acetic acid diluted in distilled water, test tube, Bunsen burner.
    • Principle: Coagulable proteins denature and form a coagulum at their isoelectric point (pI).
    • Heating proteins in an acidic medium leads to bond breaking and uncoiling of polypeptide chains, resulting in an insoluble mass.
    • No coagulation indicates non-coagulable proteins like gelatin or proteases.

    Fouchet’s Test

    • Detects bile pigments, primarily bilirubin and biliverdin, in urine.
    • Materials: Fouchet’s reagent, fresh urine, 10% barium chloride, and filter paper.
    • Principle: Ferric chloride oxidizes bilirubin to green biliverdin, producing a green precipitate.
    • Green color indicates the presence of conjugated bilirubin, confirming bile pigments in urine.
    • Increased urinary bilirubin levels can indicate conditions like obstructive or hepatocellular jaundice.

    Method for Fouchet’s Test

    • Add 5 mL of fresh urine to a test tube, mix with 2.5 mL of 10% barium chloride until a precipitate forms.
    • The development of a green color signals the presence of bile pigments, suggesting possible bilirubin-related disorders.

    Case Study Context

    • A premature infant presented with yellowish skin discoloration, likely linked to bilirubin levels, necessitating the use of Fouchet’s test for further evaluation.
    • Patient history includes a birth weight of 1.9 kg, Apgar score recorded, and administered vaccinations.

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    Description

    This quiz focuses on the Xanthoproteic test, specifically aimed at detecting aromatic amino acids like Tyrosine and Tryptophan. It covers the materials required and the procedural steps involved in conducting the test. Test your knowledge on this important biochemical reaction and its significance in amino acid analysis.

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