Carbohydrates Overview
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Questions and Answers

Which type of carbohydrate contains only one sugar unit?

  • Polysaccharides
  • Monosaccharides (correct)
  • Disaccharides
  • Oligosaccharides

    • How are monosaccharides classified based on their carbonyl group?

  • Hexoses and Pentoses
  • Aldoses and Ketoses (correct)
  • Oligosaccharides and Polysaccharides
  • Trioses and Tetroses

    • What are structural polysaccharides commonly found in combination with?

  • Hormones
  • Vitamins
  • Proteins and lipids (correct)
  • Nucleic acids

    • Which of the following correctly identifies a keto-sugar?

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

    How many carbon atoms are present in a tetrose?

    <p>4</p> Signup and view all the answers

    What is formed when dehydration reaction occurs with a pentose sugar?

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

    Which indicator is used in the test for carbohydrate solutions?

    <p>Alcoholic α-Naphthol</p> Signup and view all the answers

    Why should sulfuric acid be added slowly in the test procedure?

    <p>To prevent charring of the sugar</p> Signup and view all the answers

    What layer does the concentrated sulfuric acid form in the test tube during the procedure?

    <p>A bottom layer under the sugar solution</p> Signup and view all the answers

    What color indicates a positive result for the carbohydrate solution test?

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

    What is the main function of glucose in the human body?

    <p>It is a major source of energy for various tissues.</p> Signup and view all the answers

    Which monosaccharide is primarily associated with the formation of lactose?

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

    Which of the following is a keto pentose?

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

    Which statement regarding mannose is correct?

    <p>Mannose plays a role in glycoprotein formation.</p> Signup and view all the answers

    Which monosaccharide is used exclusively by the brain and nervous tissue for energy?

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

    What characteristic distinguishes dihydroxyacetone from other monosaccharides?

    <p>It is optically inactive.</p> Signup and view all the answers

    What is the empirical formula for carbohydrates as described?

    <p>$C_nH_{2n}O_n$</p> Signup and view all the answers

    Which of these monosaccharides can be converted into glucose in the liver?

    <p>Both A and B</p> Signup and view all the answers

    Which of the following statements regarding the structure of carbohydrates is true?

    <p>They contain a Carbonyl group, which can be either an aldehyde or a ketone.</p> Signup and view all the answers

    Which of the following statements is true about sugar classification?

    <p>All monosaccharides are sweet and soluble in water.</p> Signup and view all the answers

    What primary role do carbohydrates serve in living organisms?

    <p>They act as the main source of energy.</p> Signup and view all the answers

    In animals, carbohydrates are stored in the form of which compound?

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

    Which reaction is NOT typically characteristic of monosaccharides?

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

    Which carbohydrate is particularly noted as the main source of energy in the human body?

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

    Which of the following is NOT a role of carbohydrates in the body?

    <p>Acting solely as a source of protein.</p> Signup and view all the answers

    Which type of biological compound do carbohydrates primarily represent?

    <p>Organic compounds</p> Signup and view all the answers

    What is the significance of carbohydrates in detoxification?

    <p>They help in the elimination of drugs and toxins.</p> Signup and view all the answers

    What is the effect of acidic treatment on carbohydrate solutions in Molisch's Test?

    <p>It allows for the identification of carbohydrates.</p> Signup and view all the answers

    Which physical property describes the consistency of monosaccharide solutions?

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

    What is a common property of sugar solutions when left for a long time?

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

    Which monosaccharide is characterized as an aldo-hexose?

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

    What type of crystals can monosaccharides form when treated with phenyl hydrazine?

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

    What is a key characteristic of the clear aspect of monosaccharide solutions?

    <p>Low molecular weight</p> Signup and view all the answers

    Which of the following chemical properties is generally exhibited by both glucose and fructose?

    <p>Both can undergo oxidization reactions.</p> Signup and view all the answers

    Study Notes

    Carbohydrates

    • Organic molecules composed primarily of carbon, hydrogen, and oxygen.
    • General formula: CnH2nOnC_nH_{2n}O_nCn​H2n​On​
    • The ratio of hydrogen to oxygen is 2:1, reflecting its hydration.
    • Can be classified into monosaccharides, disaccharides, oligosaccharides, and polysaccharides based on the number of sugar units they contain.

    Properties of Carbohydrates

    • Contain a free active carbonyl group (aldehyde or ketone) responsible for their chemical activity
    • Most abundant class of organic compounds in living organisms.

    Importance of Carbohydrates

    • Primary energy source for humans and animals.
    • Essential component of the three essential food groups (along with lipids and proteins).
    • Energy storage in plants (starch) and animals (glycogen).
    • Found in cell surface receptors.
    • Structural component of DNA (deoxyribose) and RNA (ribose).
    • Play a role in detoxification, eliminating excess drugs and waste products.
    • Involved in various physiological reactions:
      • Clotting factors: Blood clotting
      • Immunoglobulins: Immunity
      • Oligosaccharides: Fertilization
    • Important for structural integrity of cellular organelles (cell membrane, mitochondria, nucleus, endoplasmic reticulum).
    • Structural polysaccharides provide support:
      • Cellulose: Plants
      • Chitin: Arthropods

    Monosaccharides

    • Simplest form of sugars
    • Cannot be broken down into simpler units
    • Building blocks for more complex carbohydrates like disaccharides and polysaccharides

    Subdividing Monosaccharides

    • By type of active carbonyl group:
      • Aldoses: Contain aldehyde (CHO) group
      • Ketoses: Contain ketone (C=O) group
    • By number of carbon atoms:
      • Trioses: 3 carbon atoms
      • Tetroses: 4 carbon atoms
      • Pentoses: 5 carbon atoms
      • Hexoses: 6 carbon atoms

    Importance of PENTOSES

    • Ribose and deoxyribose are components of nucleic acids (RNA and DNA).
    • Ribose is part of high-energy phosphate compounds like ATP, GTP, and ADP.
    • Ribose is also a component of coenzymes: NAD, NADP, FAD, FMN.

    Importance of HEXOSES

    • Glucose:
      • The primary sugar in blood and the only one used by tissues.
      • Major energy source for various tissues.
      • The sole energy source for the brain and nervous tissue.
      • Component of disaccharides and most polysaccharides.
      • Stored in the body as glycogen.
      • Can be converted into:
        • Ribose: For RNA and DNA synthesis
        • Galactose: For milk synthesis
        • Fructose: For sperm nutrition
    • Galactose:
      • Synthesized in mammary glands from glucose to form lactose in milk.
      • Obtained through lactose digestion in newborns.
      • Converted into glucose in the liver.
    • Fructose:
      • Found in fruit juice and honey.
      • The main sugar in semen, providing sperm nutrition.
      • Converted into glucose in the liver.
    • Mannose:
      • Not found in free form.
      • Important for the formation of glycoproteins and mucopolysaccharides.

    General Properties of Monosaccharides

    • Soluble in water.
    • Sweet taste.
    • Contains a symmetric carbon atom, except Dihydroxy-acetone.
    • Contains a free active group (CHO or C=O).
    • Reducing sugars.
    • Optically active compounds, except Dihydroxy-acetone.
    • Exhibit optical activity, specific rotation, and mutarotation.
    • Can be oxidized by mild and strong oxidizing agents.
    • Undergo methylation, esterification, and dehydration reactions.
    • Form osazone crystals with phenyl hydrazine.

    Identifying Carbohydrate Solutions

    • Physical properties of the solution
    • Chemical properties (tests)

    Physical Properties of Monosaccharide Solutions

    • State: Solution
    • Color: Colorless
    • Odor: Odorless when fresh (fermented solutions have an alcoholic odor)
    • Taste: Sweet
    • Solubility: Soluble in cold water
    • Reaction (pH): Neutral
    • Aspect: Clear
    • Consistency: Watery

    Chemical Properties (Tests) of Monosaccharides

    1. Molisch's Test

    • General test for the identification of all carbohydrates.

    • Sensitive, qualitative test.

    • Named after the Austrian botanist, Hans Molisch.

    • All carbohydrates give a positive result.

    • Monosaccharides react more rapidly than disaccharides and polysaccharides.

    • Chemicals:

      • Sugar solution
      • Concentrated sulfuric acid (H2SO4)
      • α-Naphthol 10%
      • Alcoholic α-Naphthol 1%

    • Principle:

      • Concentrated acid dehydrates the sugar, forming:
        • Furfural ring: Pentoses
        • Hydroxyl-Methyl-Furfural: Hexoses
      • The phenolic indicator (alcoholic α-Naphthol) reacts with the colorless furfural or hydroxyl-methyl-furfural, forming a purple-violet colored complex.

    • Procedure:

      1. Add 2 ml of glucose or fructose solution to a test tube.
      2. Add 5 drops of alcoholic 1% α-Naphthol.
      3. Shake gently.
      4. Slowly add 2 ml of concentrated sulfuric acid down the side of the inclined test tube.
      5. Observe.

    • Observation: A purple-violet ring appears between the two layers, spreading with shaking.

    • Result: Positive for carbohydrates.

    • Notes:

      • Avoid quick addition and shaking of H2SO4 to prevent charring.
      • Alcoholic α-Naphthol is an indicator, not involved in the reaction.
      • Sulfuric acid is denser than the solution, so it sinks to the bottom.

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    Carbohydrates PDF

    Description

    This quiz covers the essential aspects of carbohydrates, including their structure, properties, and importance in biological systems. You'll explore classifications such as monosaccharides and polysaccharides, and understand their crucial role as an energy source and structural component in living organisms.

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