Isolation and Tests of Carbohydrates
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Questions and Answers

What is the purpose of using 0.1% acetic acid in the isolation of carbohydrates?

  • To precipitate polysaccharides (correct)
  • To solubilize carbohydrates
  • To hydrolyze carbohydrates
  • To enhance the color in general tests

    • Which test is specifically used to detect reducing sugars and allows differentiation based on time of appearance?

  • Iodine Test
  • Mucic acid test
  • Phenylhydrazone/ Osazone Test (correct)
  • Bial’s Test

    • What is the result of a positive Molisch Test?

  • Blue solution
  • Crystals formation
  • Yellow solution
  • Purple ring at the junction of two solutions (correct)

    • Which carbohydrate is isolated from chicken liver?

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

    In the context of osazone formation, what type of sugars will produce the same osazone due to their configuration?

    <p>C-2 epimers</p> Signup and view all the answers

    What reagent is used in the Iodine Test for carbohydrates?

    <p>KI or I2</p> Signup and view all the answers

    What type of crystals are formed in a positive mucic acid test for galactose?

    <p>Galactose crystals</p> Signup and view all the answers

    What results from the condensation-oxidation-condensation reaction in the osazone test?

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

    What is the characteristic feature of osazone formed from D-glucose when reacting with phenylhydrazine?

    <p>It appears as yellow-colored crystals.</p> Signup and view all the answers

    Which method is used for the extraction of starch from potato during the isolation of carbohydrates?

    <p>Chopping and grinding</p> Signup and view all the answers

    What is the positive result of the Iodine Test used for identifying carbohydrates?

    <p>Appearance of a blue solution.</p> Signup and view all the answers

    Which carbohydrates will yield the same osazone due to their structural similarities during the osazone test?

    <p>Glucose and fructose.</p> Signup and view all the answers

    What is the main principle of the Phenylhydrazone/Osazone Test?

    <p>It detects carbonyl groups in carbohydrates.</p> Signup and view all the answers

    Which result indicates a positive outcome during the Molisch Test for carbohydrates?

    <p>Appearance of a purple ring at the interface.</p> Signup and view all the answers

    What type of crystals are formed as a result of the Mucic acid test for galactose?

    <p>Colorless needle-like crystals.</p> Signup and view all the answers

    Which of the following reagents is specifically used in the Bial’s Test for carbohydrates?

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

    Which carbohydrate can be isolated from potato using the described extraction method?

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

    What is the observable result of a positive Iodine Test for carbohydrates?

    <p>Blue solution</p> Signup and view all the answers

    In the osazone test, which sugar configuration will yield different osazones due to the reaction with phenylhydrazine?

    <p>D-glucose and D-fructose</p> Signup and view all the answers

    Which test provides a visual indicator of the presence of reducing sugars through the formation of yellow crystalline structures?

    <p>Phenylhydrazone/Osazone test</p> Signup and view all the answers

    What role does 5% α-napthol in ethanol play in carbohydrate testing?

    <p>Reacts to form a positive Molisch test result</p> Signup and view all the answers

    During the mucic acid test, which of the following would confirm the presence of galactose?

    <p>Precipitation of galactose crystals</p> Signup and view all the answers

    Which significant feature distinguishes osazones from different reducing sugars?

    <p>Shape and melting point of crystals</p> Signup and view all the answers

    Which method of carbohydrate isolation involves settling as a key step?

    <p>Chopping and grinding</p> Signup and view all the answers

    Study Notes

    Isolation of Carbohydrates

    • Chicken Liver is used to isolate Glycogen
      • Liver is minced and blended before being extracted with 0.1% acetic acid
      • Glycogen is precipitated with ethanol
    • Potato is used to isolate Starch
      • Potato is chopped and ground before being extracted
      • Starch is isolated by settling, making use of its density

    General Tests for Carbohydrates

    • Molisch Test

      • Uses Molisch reagent (5% α-napthol in 95% ethanol)
      • Positive Result: Purple ring forms at the junction of the two solutions

    • Iodine Test

      • Uses KI or I2 (potassium iodide or iodine)
      • Positive Result: Blue solution

    Qualitative Tests for Carbohydrates

    • Bial’s Test

      • Used to identify pentoses

    • Mucic Acid Test

      • Used to identify galactose
      • Involves formation of mucic acid crystals

    • Phenylhydrazone/Osazone Test

      • Used to detect reducing sugars
      • Different reducing sugars form osazones with characteristic shapes and times of formation
      • Osazone formation occurs through a reaction between a sugar and phenylhydrazine
      • Principle: The reaction forms a 1, 2-diphenyhydrazone known as osazone, which has unique characteristics for each sugar.
      • Osazone is different for different sugars, so it can help with identification
      • C-2 epimers (sugars that differ only in the configuration at carbon 2) form the same osazone
      • Ketoses with similar configurations below C-2 to aldoses also form the same osazones (example: glucose and fructose)

    Carbohydrate Isolation & Characterization

    • Isolation: Different methods used for isolating carbohydrates from natural sources
      • Chicken Liver (Glycogen):
        • Extraction: Minced liver blended with 0.1% acetic acid for precipitation
      • Potato (Starch):
        • Extraction: Chopped potato is ground, starch settles at the bottom
    • General Tests for Carbohydrates:
      • Molisch Test:
        • Reagent: 5% α-napthol in 95% ethanol
        • Positive Result: Purple ring at the junction of the two solutions
      • Iodine Test:
        • Reagent: KI or I2
        • Positive Result: Blue solution
    • Acid Hydrolysis: Breaks down polysaccharides into simpler sugars
      • Qualitative Tests: Used to identify specific sugars after hydrolysis

    Qualitative Tests for Carbohydrates

    • Bial's Test: Detects pentoses (especially arabinose)
      • Positive Result: Green-colored solution
      • Differentiates pentoses from hexoses
    • Mucic Acid Test: Detects galactose
      • Positive Result: White, crystalline precipitate of mucic acid
    • Phenylhydrazone/ Osazone Test:
      • Reagent: Phenylhydrazine in acetate buffer
      • Positive Result: Formation of yellow-colored crystalline osazones
      • Allows differentiation of reducing sugars based on osazone formation time and characteristics
    • Procedure:
      • Reducing sugars react with phenylhydrazine to form osazones
      • Formation of osazone is unique for specific sugars
        • Glucose and fructose produce the same osazone
        • C-2 epimers of sugars produce the same osazone
      • Osazones are characterized by:
        • Characteristic shape
        • Solubility
        • Melting point
        • Time of formation

    Isolation of Carbohydrates

    • Chicken Liver - glycogen
      • Minced and blended
      • 0.1% acetic acid added to precipitate glycogen
      • Extracted with Ethanol
    • Potato - starch
      • Chopped and ground
      • Starch settles

    General Tests for Carbohydrates

    • Molisch Test
      • Uses Molisch reagent (5% α-napthol in 95% ethanol)
      • Positive result: purple ring at the junction of the two solutions
    • Iodine Test
      • Uses KI or I2
      • Positive result: blue solution

    Qualitative Tests for Carbohydrates

    • Bial's Test
      • Differentiates pentose from hexose sugars
      • Pentose sugars react with Bial's reagent, a solution containing orcinol and iron chloride in concentrated hydrochloric acid
      • Hexose sugars do not react with Bial's reagent
    • Mucic Acid Test for Galactose
      • Uses nitric acid
      • Positive result: formation of white, crystalline mucic acid
    • Phenylhydrazone/ Osazone Test
      • Used to detect reducing sugars
      • Different reducing sugars can be differentiated based on the timing of the complex formation
      • Phenylhydrazine in acetate buffer reacts with free or potentially free carbonyl groups of carbohydrates, forming osazones
      • Osazones are yellow crystals with a characteristic shape, solubility, melting point and time of formation
      • Osazone formation is distinct for different sugars
      • C-2 epimers produce the same osazone
      • Ketoses with a configuration identical to aldoses below C-2 give the same osazones, e.g glucose and fructose

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    Carbohydrate Isolation and Characterization Activity 5 PDF

    Description

    Explore the isolation techniques and general tests for carbohydrates in this quiz. Learn about the methods used to extract glycogen from chicken liver, isolate starch from potatoes, and perform various qualitative tests. Test your knowledge on carbohydrate chemistry and their characteristics.

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