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Questions and Answers
What type of test is Molisch's test classified as?
What type of test is Molisch's test classified as?
Which sugars are classified as reducing sugars?
Which sugars are classified as reducing sugars?
Which carbohydrate is not classified as a sugar?
Which carbohydrate is not classified as a sugar?
What determines whether a monosaccharide is classified as an aldose or a ketose?
What determines whether a monosaccharide is classified as an aldose or a ketose?
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What indicates the presence of carbohydrates when using alcoholic alpha naphthol?
What indicates the presence of carbohydrates when using alcoholic alpha naphthol?
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Which of the following substances is known to function as a storage polysaccharide?
Which of the following substances is known to function as a storage polysaccharide?
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What color change is observed in the Anthrone test for carbohydrates?
What color change is observed in the Anthrone test for carbohydrates?
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What is the common molecular ratio of hydrogen to oxygen in carbohydrates?
What is the common molecular ratio of hydrogen to oxygen in carbohydrates?
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Which reagent is used in the Iodine test for detecting polysaccharides?
Which reagent is used in the Iodine test for detecting polysaccharides?
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Which test is NOT used to detect the reducing properties of sugars?
Which test is NOT used to detect the reducing properties of sugars?
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Which of the following statements is true about carbohydrates?
Which of the following statements is true about carbohydrates?
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What happens if concentrated organic solutions are tested with sulfuric acid?
What happens if concentrated organic solutions are tested with sulfuric acid?
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Which of the following does NOT form a complex with iodine during testing?
Which of the following does NOT form a complex with iodine during testing?
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The reaction between furfural and which agent results in a colored complex during the Anthrone test?
The reaction between furfural and which agent results in a colored complex during the Anthrone test?
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What is the role of potassium iodide in the iodine reagent?
What is the role of potassium iodide in the iodine reagent?
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In the Iodine test, a blue color indicates the presence of which carbohydrate?
In the Iodine test, a blue color indicates the presence of which carbohydrate?
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What color indicates the presence of ketoses in the Seliwanoff's test?
What color indicates the presence of ketoses in the Seliwanoff's test?
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What is detected by Fehling's test?
What is detected by Fehling's test?
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Which of the following statements about Seliwanoff's reagent is false?
Which of the following statements about Seliwanoff's reagent is false?
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What happens to glucose when prolonged boiling occurs in Seliwanoff's test?
What happens to glucose when prolonged boiling occurs in Seliwanoff's test?
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What role does Rochelle salt play in Fehling's test?
What role does Rochelle salt play in Fehling's test?
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How does Benedict's test differ from Fehling's test?
How does Benedict's test differ from Fehling's test?
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What indicates a positive result in Benedict's test?
What indicates a positive result in Benedict's test?
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What is the primary visual indicator of reducing sugars during Fehling's test?
What is the primary visual indicator of reducing sugars during Fehling's test?
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Study Notes
Qualitative Tests of Carbohydrates
- Carbohydrates are essential components of food, primarily obtained as starch from plants.
- In the body, glucose is utilized or stored as glycogen.
- Carbohydrates consist of carbon, hydrogen, and oxygen atoms, usually in a 2:1 ratio to hydrogen as in water.
- Classified into monosaccharides (cannot be further hydrolyzed), oligosaccharides (hydrolyze into 2-10 monosaccharides), and polysaccharides (hydrolyze into numerous monosaccharides).
- Monosaccharides are further categorized by the number of carbon atoms (e.g., hexose) and functional group (aldose or ketose).
- Sugars are either reducing (e.g., glucose, fructose) or non-reducing (e.g., sucrose).
- Reducing properties of sugars are tested using Fehling's, Benedict's, and Tollen's tests.
- Molisch's test, Anthrone test, Iodine test, Seliwanoff's test, Picric acid test, Mucic acid test, Bial's test, and Osazone test are specific tests for different carbohydrate types.
Molisch's Test
- A general test for carbohydrates.
- Concentrated sulfuric acid reacts with carbohydrates to produce furfural derivatives
- These derivatives react with α-naphthol to form a reddish-violet ring.
- Polysaccharides and glycoproteins exhibit positive results.
Anthrone Test
- Another general test for carbohydrates.
- Furfural produced in the reaction with concentrated sulfuric acid reacts with anthrone.
- Results in bluish-green complex formation.
Iodine Test
- Specifically tests for starch and related substances like glycogen.
- Starch reacts with iodine to form a dark blue/black color.
- Glycogen exhibits reddish-brown color with iodine.
Seliwanoff's Test
- Differentiates between aldoses and ketoses.
- Ketoses, particularly fructose, react rapidly to yield a reddish-colored complex.
- Aldoses, such as glucose, react more slowly to produce a weaker or negative result.
Fehling's and Benedict's Tests
- Detects reducing sugars.
- Reducing sugars reduce copper ions in Fehling's and Benedict's solutions.
- This reduction is visually detected by a red or orange precipitate.
- Benedict's test is considered more convenient and stable than Fehling's.
Picric Acid Test
- Detects reducing sugars.
- Reducing sugars react with picric acid in alkaline medium to form a red colored picramic acid.
Bial's Test
- Specific for pentose sugars.
- Reaction yields a blue-green colored complex in the presence of pentoses.
Osazone Test
- Distinguishes different sugars by forming specific crystal structures.
- Identifies reducing sugars.
Tollen's Test
- Identifies reducing sugars using ammoniacal silver nitrate solution
- Reducing sugars form a silver mirror on the test tube walls.
Reduction Tests (Including Phenylhydrazine)
- Carbohydrates with aldehyde/ketone groups reduce metallic ions in solution.
- Tests help confirm reducing sugar identities.
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Description
Explore the qualitative tests used to identify different types of carbohydrates, including sugars. This quiz covers classifications such as monosaccharides, oligosaccharides, and polysaccharides, as well as various testing methods like Molisch's test and Benedict's test. Test your knowledge of carbohydrate chemistry and its importance in biology.
