Carbohydrates: Basic Composition and Classification
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Questions and Answers

What is the basic composition of carbohydrates?

  • (CNOH)n
  • (CH2O)n (correct)
  • (CHNO)
  • (CH2NO)n

    • What is a monosaccharide?

  • A simple sugar with multiple OH groups (correct)
  • A few monosaccharides covalently linked
  • Two monosaccharides covalently linked
  • A complex sugar with one OH group

    • What is the chemical formula for glucose?

  • C6H10O5
  • C5H10O5
  • C5H12O6
  • C6H12O6 (correct)

    • Which sugar has the highest relative sweetness?

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

    What type of group do aldoses have at one end?

    <p>Aldehyde group</p> Signup and view all the answers

    What is the simplest of the aldoses?

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

    Which term describes the varying sweetness of different monosaccharides?

    <p>Arrangement differences</p> Signup and view all the answers

    What does it mean when a sugar solution is described as dextrorotatory?

    <p>It turns the plane of polarized light to the right</p> Signup and view all the answers

    What type of bond is formed when the anomeric hydroxyl and another compound join together?

    <p>Glycosidic bond</p> Signup and view all the answers

    Which sugar derivative has an amino group that substitutes for a hydroxyl group?

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

    What type of form does methyl-D-glucoside take when reacting with methanol?

    <p>$\alpha$-D-glucopyranose</p> Signup and view all the answers

    What accounts for the differences in sweetness among glucose, fructose, and galactose?

    <p>Carbon chain length</p> Signup and view all the answers

    What type of glycosidic bond holds together two glucose units in maltose?

    <p>α(1→4)</p> Signup and view all the answers

    Which disaccharide is composed of galactose & glucose with a β(1→4) glycosidic linkage?

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

    What is the product of cellulose breakdown that is the equivalent β anomer of maltose?

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

    Which disaccharide has a glycosidic bond linking the anomeric hydroxyls of glucose & fructose?

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

    What type of glycosidic bond holds together α-D-glucose &β-D-fructose units in sucrose?

    <p>(α1→2)</p> Signup and view all the answers

    What is the full name of lactose?

    <p>β-D-galactopyranosyl-(1→4)α-D-glucopyranose</p> Signup and view all the answers

    What is the relationship between two aldotetroses that are stereoisomers and mirror images of each other?

    <p>They are enantiomers</p> Signup and view all the answers

    What type of reaction occurs when an aldehyde reacts with an alcohol?

    <p>Hemiacetal formation</p> Signup and view all the answers

    What is the difference between a hemiacetal and a hemiketal?

    <p>A hemiacetal is formed from an aldehyde and a hemiketal is formed from a ketone</p> Signup and view all the answers

    What are anomers?

    <p>Stereoisomers formed when a ring is formed</p> Signup and view all the answers

    What is the rule for drawing the highest numbered carbon for D-sugars in Haworth projections?

    <p>It is drawn up</p> Signup and view all the answers

    What is the relationship between two aldohexoses that differ only in the position of the hydroxyl group on one asymmetric carbon (carbon 4)?

    <p>They are epimers</p> Signup and view all the answers

    Which sugar is the principal sugar in milk?

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

    Which of the following sugars is a non-reducing sugar?

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

    What happens to the rotation of sucrose in solution when it is hydrolyzed?

    <p>It changes from dextrorotatory to levorotatory</p> Signup and view all the answers

    Which polysaccharide is the most common storage polysaccharide in plants?

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

    What is the primary polymeric form of glucose storage in plants?

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

    Which type of amylose is a glucose polymer with α(1→4) linkages?

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

    Study Notes

    Carbohydrates (Glycans)

    • General composition: (CH2O)n
    • Classified into four categories: monosaccharides, disaccharides, oligosaccharides, and polysaccharides

    Monosaccharides (Simple Sugars)

    • Characteristics:
      • Energy-containing molecules
      • Provide structure
      • Basic building block: (CH2O)n; n = 3, 5, 6
      • Classified by number of carbons and type (aldose or ketose)
    • Examples:
      • Glucose (C6H12O6)
      • Fructose
      • Galactose
      • D-glyceraldehyde (simplest aldose)

    Disaccharides

    • Definition: 2 monosaccharides covalently linked
    • Examples:
      • Maltose (α-D-glucose units linked by α(1→4) glycosidic bond)
      • Sucrose (α-D-glucose and β-D-fructose units linked by α(1→2) glycosidic bond)
      • Lactose (β-D-galactose and β-D-glucose units linked by β(1→4) glycosidic bond)

    Glycosidic Bonds

    • Formation: anomeric hydroxyl and a hydroxyl of another sugar or compound join together, splitting out water
    • Example: methanol reacts with the anomeric OH on glucose to form methyl glucoside

    Sugar Derivatives

    • Amino sugars: an amino group substitutes for a hydroxyl (e.g., glucosamine)
    • Acetylated amino sugars: amino group may be acetylated (e.g., N-acetylglucosamine)

    Optical Activity

    • Dextrorotatory (+): sugar solution turns the plane of polarized light to the right
    • Levorotatory (-): sugar solution turns the plane of polarized light to the left
    • Racemic mixture: equimolar mixture of optical isomers has no net rotation

    Polysaccharides

    • Definition: polymers consisting of chains of monosaccharide or disaccharide units
    • Examples:
      • Starch (plant storage polysaccharide, composed of amylose and amylopectin)
      • Amylose (glucose polymer with α(1→4) linkages)
      • Amylopectin (glucose polymer with varying lengths and molecular weights)

    Miscellaneous

    • Relative sweetness of different sugars:
      • Sucrose: 100
      • Glucose: 74
      • Fructose: 174
      • Lactose: 16
      • Invert Sugar: 126
      • Maltose: 32
      • Galactose: 32
    • Hemiacetal and hemiketal formation: reaction between an aldehyde or ketone and an alcohol to form a hemiacetal or hemiketal, respectively

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    Description

    Learn about the basic composition of carbohydrates (glycans) with the general formula (CH2O)n. Explore the classification of carbohydrates into monosaccharides, disaccharides, oligosaccharides, and polysaccharides based on the number of carbons in the molecules.

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