Carbohydrates and Their Types
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Questions and Answers

What type of sugar is identified as a ketohexose in the test results?

  • Xylose
  • Fructose (correct)
  • Glucose
  • Sucrose

    • What color indicates a positive reaction for aldohexoses in the results?

  • Yellow
  • Red
  • Pink (correct)
  • Blue Green

    • What chemical is NOT part of Benedict’s reagent?

  • Resorcinol (correct)
  • Sodium carbonate
  • Sodium citrate
  • Copper sulfate

    • Which of the following sugars did NOT show any reaction according to the provided results?

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

    Which test is specifically used to differentiate ketohexoses from aldohexoses?

    <p>Seliwanoff's Test</p> Signup and view all the answers

    What is formed when two monosaccharides combine?

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

    Which type of carbohydrate is known for being highly soluble in water?

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

    Which reagent is used in the Molisch test for carbohydrates?

    <p>Molisch Reagent</p> Signup and view all the answers

    What color indicates the presence of glucose in the Molisch test?

    <p>Purple ring</p> Signup and view all the answers

    What is a common feature of polysaccharides?

    <p>They can serve as structural or storage compounds.</p> Signup and view all the answers

    Which carbohydrate is known as 'milk sugar'?

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

    What is the role of sulfuric acid in the dehydration process of sugars?

    <p>It forms a lower layer in the test tube.</p> Signup and view all the answers

    Which of the following is a storage polysaccharide?

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

    Which of the following is NOT a monosaccharide mentioned in the content?

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

    Which category does not belong to the classification of carbohydrates?

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

    What is the main principle behind the formation of furfural from sugars?

    <p>Dehydration of sugars</p> Signup and view all the answers

    Which carbohydrate is a combination of fructose and glucose?

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

    Which of the following results is observed for distilled water in the Molisch test?

    <p>Absence of any color</p> Signup and view all the answers

    What type of compound is formed from the combination of furfural with phenolic compounds?

    <p>Colored condensation products</p> Signup and view all the answers

    What distinguishes reducing sugars from other carbohydrates?

    <p>They can undergo oxidation.</p> Signup and view all the answers

    Which of the following describes a characteristic of disaccharides?

    <p>Formed from two monosaccharides</p> Signup and view all the answers

    What type of sugar does Bial's Orcinol test specifically confirm?

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

    What color indicates a positive reaction for ketoses when using Bial's Orcinol test?

    <p>Cherry Red</p> Signup and view all the answers

    Which reagent is added after heating in the procedure for Bial's Orcinol test?

    <p>FeCl3 solution</p> Signup and view all the answers

    How is the test result assessed after the Bial's Orcinol test is performed?

    <p>By observing color changes</p> Signup and view all the answers

    What potential interference might occur during the Bial's Orcinol test?

    <p>Presence of heptoses</p> Signup and view all the answers

    In the Bial's Orcinol test, what is the effect of adding concentrated H2SO4?

    <p>It dehydrates the sugar</p> Signup and view all the answers

    Which product is formed from aldohexoses during the Bial's Orcinol test?

    <p>Hydroxymethyl-furfural</p> Signup and view all the answers

    What initial preparation step is required before adding the reagents in the Bial's Orcinol test?

    <p>Heat the solution to a specific temperature</p> Signup and view all the answers

    What is used to dilute the mixture to make 50 mL in the isolation procedure of RNA?

    <p>0.2% NaOH solution</p> Signup and view all the answers

    At what temperature and duration should the beaker be heated in the water bath?

    <p>90°C for 30 minutes</p> Signup and view all the answers

    Which equipment is NOT mentioned as part of the RNA isolation procedure?

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

    What types of tests are performed on the filtrate after cooling?

    <p>Qualitative tests for nucleoproteins</p> Signup and view all the answers

    Which chemical is specifically used in Biuret's test for detecting nucleoproteins?

    <p>Copper sulfate (CuSO4)</p> Signup and view all the answers

    Which of the following substances is NOT involved in the isolation process of RNA from yeast?

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

    What precipitates from an alkaline solution when acid is added?

    <p>Alkali metal salts</p> Signup and view all the answers

    Which of the following represents a step in filtering the RNA extract?

    <p>Filtering once through cheesecloth and thrice through filter paper</p> Signup and view all the answers

    Study Notes

    Carbohydrates

    • Polyhydroxy aldehyde or ketone or a compound that yields polyhydroxy aldehydes and polyhydroxy ketones on hydrolysis.
    • Commonly known as sugars because most of them have a sweet taste.
    • Serves as a major source of energy.
    • Furnishes the carbon chains of compound synthesis.
    • Found in nature and function either as:
      • Bioorganic compounds
        • Proteins
        • Lipids
        • Nucleic Acids
      • Categorized as
        • Monosaccharides
        • Disaccharides
        • Polysaccharides

    Monosaccharides

    • Highly soluble in water.
    • Less soluble in ethanol.
    • Insoluble in ether.
    • Aldoses or ketoses.
    • Free monosaccharides are all reducing sugars.

    Disaccharides

    • Formed by two molecules of monosaccharides.
    • Examples include:
      • Maltose (Glucose + Glucose) – abundant in germinating barley.
      • Sucrose (Fructose + Glucose) – also known as table sugar / cane sugar / beet sugar.
      • Lactose or Milk Sugar (Galactose + Glucose) – does not taste very sweet and is not fermented by yeast.

    Polysaccharides

    • Structural polysaccharide:
      • Cellulose
    • Storage polysaccharide:
      • Starch
      • Dextrin
      • Glycogen
      • Insulin

    Midterm Lab: Carbo Part 1 - Tests Based on Furfural & Its Derivatives

    • Tests are based on furfural and its derivatives.
    • Principle: Hot H2SO4 will dehydrate sugars into furfural and its derivatives.

    Molisch Test

    • General test for carbohydrates.
    • Molisch reagent contains 𝛂-naphthol.
    • Positive result: formation of purple ring.
    • Concentrated H2SO4 will dehydrate the sugar, allowing it to react with the alcohol forming furfural or hydroxymethyl-furfural.

    Bial’s Orcinol Test

    • Determines the presence of pentoses, but not specific.
    • Distinguishes pentose monosaccharide and hexose monosaccharide.
    • The reaction is not specific for pentoses because other compounds like trioses, uronic acids, and certain heptoses will also give blue or green products.
    • Positive result:
      • Pentoses + Orcinol → Blue Green Compound (HCl & Resorcinol)
      • Ketohexoses + Condensation Product → Cherry Red
      • Hexoses + Orcinol → Yellow Brown Pigment (HCl & Resorcinol)
      • Aldohexoses + Condensation Product → Pale Pink

    Seliwanoff’s Test

    • Used to differentiate ketohexoses from aldohexoses.
    • Ketohexoses react faster with the solution of hydrochloric acid and resorcinol than aldohexoses.
    • Positive result:
      • Ketohexoses reaction: Cherry Red
      • Aldohexoses reaction: Pale Pink

    Midterm Lab: Carbo Part 2 — Tests Based on the Reducing Properties of Sugars

    • Used for sugars with aldehydes.
    • Benedict's reagent:
      • CuSO4 (copper sulfate)
      • Na2CO3 (sodium carbonate)
      • Na3C6H5O7 sodium citrate
    • Positive compounds:
      • Brick Red Precipitate Cu2O (copper)

    Isolation of RNA from Yeast

    • To isolate RNA from yeast.
    • To test properties of the isolated RNA.
    • Procedure:
      1. Add 10 g of baker’s yeast in a mortar.
      2. Grind the yeast with 5 ml of 0.2% NaOH using a pestle.
      3. Pour the mixture in a beaker and dilute with 0.2% NaOH solution to make 50 mL.
      4. Cover the beaker with a watch glass to avoid evaporation.
      5. Heat the beaker in a water bath with a constant temperature of 90°C for 30 minutes.
      6. Filter the solution thrice using cheesecloth and once through a filter paper.
      7. Allow the filtrate to cool → RNA EXTRACT (RE).
      8. Perform the following tests on the filtrate (RE).

    Qualitative Tests: Test for Nucleoproteins (Biuret’s Test)

    • Nucleoproteins are any proteins that are structurally associated with nucleic acids either DNA or RNA.
    • Procedure:
      1. Add 1 mL of the filtrate (RE) in a test tube.
      2. Add 2 drops of 10% NaOH.
      3. Add 2 drops of 1% CuSO4 (copper sulfate solution).

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    Biochemistry Lab Midterm - Carbohydrates PDF

    Description

    This quiz covers the fundamentals of carbohydrates, including their definitions, classifications, and individual types such as monosaccharides and disaccharides. Understanding carbohydrates is crucial as they are a major energy source and play significant roles in biological compounds.

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