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Questions and Answers
Which of the following substances, when present in saliva, would be expected to yield a positive result with Benedict's reagent after the addition of NaOH and heat?
Which of the following substances, when present in saliva, would be expected to yield a positive result with Benedict's reagent after the addition of NaOH and heat?
Which of the following tests would produce a distinctive color change indicative of the presence of proteins in saliva?
Which of the following tests would produce a distinctive color change indicative of the presence of proteins in saliva?
A sample of saliva is tested with the following reagents: H₂SO₄, KI, and starch. What would be the expected result if the saliva contained a significant amount of nitrate?
A sample of saliva is tested with the following reagents: H₂SO₄, KI, and starch. What would be the expected result if the saliva contained a significant amount of nitrate?
A red color is observed when testing saliva with FeCl₃ and HCl. This indicates the presence of which substance in the saliva?
A red color is observed when testing saliva with FeCl₃ and HCl. This indicates the presence of which substance in the saliva?
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Which of the following substances is NOT a typical constituent of saliva, according to the information provided?
Which of the following substances is NOT a typical constituent of saliva, according to the information provided?
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Which of the following tests would produce a yellow precipitate as a positive result?
Which of the following tests would produce a yellow precipitate as a positive result?
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Which of the following substances in saliva, upon reacting with NaOH and CuSO₄, would exhibit a distinctive color change characteristic of a positive Biuret test?
Which of the following substances in saliva, upon reacting with NaOH and CuSO₄, would exhibit a distinctive color change characteristic of a positive Biuret test?
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If a sample of saliva is tested with Benedict's solution and heated, resulting in a brick-red precipitate, what can be inferred about the presence of carbohydrates in the saliva?
If a sample of saliva is tested with Benedict's solution and heated, resulting in a brick-red precipitate, what can be inferred about the presence of carbohydrates in the saliva?
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In the presence of which of the following substances would a sample of saliva, when treated with HNO₃ and AgNO₃, produce a white precipitate?
In the presence of which of the following substances would a sample of saliva, when treated with HNO₃ and AgNO₃, produce a white precipitate?
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The presence of which of the following substances in saliva is often attributed to smoking or certain medications?
The presence of which of the following substances in saliva is often attributed to smoking or certain medications?
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Which of the following statements accurately describes the expected results of a test for nitrate in saliva?
Which of the following statements accurately describes the expected results of a test for nitrate in saliva?
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Which of the following substances is a normal constituent of saliva and is detected by the formation of a yellow precipitate when reacting with ammonium molybdate?
Which of the following substances is a normal constituent of saliva and is detected by the formation of a yellow precipitate when reacting with ammonium molybdate?
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Study Notes
Testing Substances in Saliva
-
Carbohydrates:
- Detected using NaOH and Benedict's solution followed by heat.
- Positive result indicated by a brick-red precipitate, confirming the presence of carbohydrates as mucin is a glycoprotein that hydrolyzes to reducing sugars.
-
Proteins:
- Identified via NaOH and CuSO₄ (Biuret test).
- A violet color indicates a positive result, affirming the presence of proteins in mucin.
-
Nitrate:
- Tested using H₂SO₄, KI, and starch.
- No significant color change implies that saliva usually lacks substantial nitrate levels; it is not a common component.
-
Thiocyanate:
- Detected with FeCl₃ and HCl.
- A red color forms, indicating thiocyanate ions present, often linked to smoking or certain medications.
-
Glucose:
- Tested using Benedict's solution and heat.
- Positive test shown by a brick-red precipitate; glucose is typically found in saliva after ingestion, influenced by diet and glucose metabolism.
-
Inorganic Phosphate:
- Identified through ammonium molybdate.
- A yellow precipitate confirms phosphate ions, a standard constituent of saliva.
-
Chloride:
- Tested with HNO₃ and AgNO₃.
- Formation of a white precipitate indicates chloride ions, which are commonly found in saliva.
Testing Substances in Saliva
-
Carbohydrates:
- Detected using NaOH and Benedict's solution followed by heat.
- Positive result indicated by a brick-red precipitate, confirming the presence of carbohydrates as mucin is a glycoprotein that hydrolyzes to reducing sugars.
-
Proteins:
- Identified via NaOH and CuSO₄ (Biuret test).
- A violet color indicates a positive result, affirming the presence of proteins in mucin.
-
Nitrate:
- Tested using H₂SO₄, KI, and starch.
- No significant color change implies that saliva usually lacks substantial nitrate levels; it is not a common component.
-
Thiocyanate:
- Detected with FeCl₃ and HCl.
- A red color forms, indicating thiocyanate ions present, often linked to smoking or certain medications.
-
Glucose:
- Tested using Benedict's solution and heat.
- Positive test shown by a brick-red precipitate; glucose is typically found in saliva after ingestion, influenced by diet and glucose metabolism.
-
Inorganic Phosphate:
- Identified through ammonium molybdate.
- A yellow precipitate confirms phosphate ions, a standard constituent of saliva.
-
Chloride:
- Tested with HNO₃ and AgNO₃.
- Formation of a white precipitate indicates chloride ions, which are commonly found in saliva.
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Description
This quiz tests your understanding of biochemistry lab procedures and results, specifically the testing of mucin for carbohydrates and proteins using various reagents and expected results.
