Carbohydrates Overview
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Questions and Answers

What type of bond is formed when two monosaccharides join together?

  • Peptide bond
  • Ionic bond
  • Disulfide bond
  • O-glycosidic bond (correct)

    • Which of the following disaccharides is classified as a reducing sugar?

  • Lactose
  • Sucrose
  • Maltose (correct)
  • Trehalose

    • What is the primary function of sucrose in plants?

  • The principal form of sugar transported from leaves (correct)
  • Building structural components in cell walls
  • Energy storage in roots
  • Enhancing water absorption

    • Which of the following sugars results from the hydrolysis of lactose?

    <p>D-galactose and D-glucose (A)</p> Signup and view all the answers

    What is a characteristic of the configuration of the anomeric carbon atom in maltose?

    <p>It is in its alpha configuration (A)</p> Signup and view all the answers

    What configuration indicates that a sugar is a D isomer?

    <p>The hydroxyl group is on the right in the projection formula. (B)</p> Signup and view all the answers

    Which of the following pairs of sugars are considered epimers?

    <p>D-glucose and D-mannose (B)</p> Signup and view all the answers

    What type of bond is formed during the reaction of monosaccharides to create disaccharides?

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

    In the context of cyclic monosaccharides, what does the term 'anomeric carbon' refer to?

    <p>The carbon that is derived from the carbonyl carbon. (B)</p> Signup and view all the answers

    What is mutarotation in relation to monosaccharides?

    <p>The reversible change in the configuration of the anomeric carbon. (C)</p> Signup and view all the answers

    What are the primary functions of carbohydrates in the body?

    <p>Storage form of energy and cell membrane components (D)</p> Signup and view all the answers

    Which of the following correctly describes monosaccharides?

    <p>Single polyhydroxy aldehyde or ketone units (A)</p> Signup and view all the answers

    What type of bond connects monosaccharide units in oligosaccharides?

    <p>Glycosidic bonds (A)</p> Signup and view all the answers

    Which of the following polysaccharides is known for having a branched structure?

    <p>Glycogen (C)</p> Signup and view all the answers

    What is the significance of the empirical formula (CH2O)n for carbohydrates?

    <p>It shows the ratio of hydrogen to oxygen in carbohydrates. (B)</p> Signup and view all the answers

    What property is NOT commonly associated with carbohydrates?

    <p>Freely soluble in nonpolar solvents (D)</p> Signup and view all the answers

    How many stereoisomers can a sugar molecule with 4 chiral centers have?

    <p>16 stereoisomers (B)</p> Signup and view all the answers

    Which of the following statements about disaccharides is true?

    <p>They are composed of monosaccharides connected by glycosidic bonds. (A)</p> Signup and view all the answers

    Flashcards

    Stereochemistry

    The arrangement of atoms in a molecule, specifically focusing on the position of groups relative to a chiral center.

    D-Isomer

    A sugar molecule with the hydroxyl group on the right side of the reference carbon in a Fischer projection, with the carbonyl carbon at the top.

    L-Isomer

    A sugar molecule with the hydroxyl group on the left side of the reference carbon in a Fischer projection, with the carbonyl carbon at the top.

    Epimers

    Two sugar molecules differing only in the configuration around one specific carbon atom.

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    Mutarotation

    The process by which the cyclic forms of monosaccharides interconvert in solution, resulting in a mixture of anomers at equilibrium.

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    Disaccharide

    A type of sugar molecule composed of two simpler sugar units (monosaccharides) linked together by a covalent bond.

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    O-glycosidic bond

    A specific type of covalent bond that links two sugar (monosaccharide) molecules together in a disaccharide, formed by the reaction between the anomeric carbon of one sugar and a hydroxyl group of the other.

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    Anomeric carbon

    The carbon atom in a sugar molecule that can exist in either an alpha or beta configuration, affecting the sugar's reactivity.

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    Reducing sugar

    A sugar that can donate electrons and reduce another molecule, typically an oxidizing agent. It has a free anomeric carbon.

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    Maltose

    A type of disaccharide made up of two glucose molecules joined by an alpha-1,4-glycosidic bond. It's a reducing sugar.

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    Carbohydrates

    The most abundant organic molecules found in nature with diverse functions, they provide dietary calories, serve as energy storage, and act as structural components.

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    Monosaccharides

    Sugars with a single polyhydroxy aldehyde or ketone unit, can be either linear or cyclic, and are classified based on the number of carbon atoms.

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    Oligosaccharides

    Short chains of monosaccharides linked together by glycosidic bonds, they are made up of two to ten monosaccharide units.

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    Polysaccharides

    A large class of carbohydrates composed of many monosaccharides linked together by glycosidic bonds, often forming long chains, both linear and branched.

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    Glycogen

    A type of polysaccharide with important functions in energy storage, it is a branched structure composed of glucose units.

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    Cellulose

    A type of polysaccharide that forms the structural framework of plant cell walls, it is a linear chain of glucose units.

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    Glyceraldehyde

    A three-carbon sugar, it is the simplest aldose and serves as a reference point for understanding the stereochemistry of sugars.

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    Fischer Projections

    A way to represent three-dimensional sugar structures on paper, horizontal bonds project towards the reader and vertical bonds project away from the reader.

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    Study Notes

    Carbohydrates

    • Abundant organic molecules in nature
    • Serve many functions, including energy storage, acting as components of cell membranes, and structural components such as cell walls of bacteria, insect exoskeletons, and plant cellulose.
    • They are polyhydroxy aldehydes or ketones, or substances that yield such compounds on hydrolysis.
    • Empirical formula (CH₂O)ₙ; some also contain N, P, or S.

    Classes of Carbohydrates

    • Monosaccharides (simple sugars)
    • Oligosaccharides (short chains)
    • Polysaccharides (sugar polymers)
    • Sakcharon—> saccharides

    Monosaccharides

    • Consist of a single polyhydroxy aldehyde or ketone unit
    • Glucose (sometimes called dextrose).
    • Four or more carbons tend to have cyclic structures.
    • Two Families:
      • Aldoses (backbone)
      • Ketoses (three-carbon trioses)
    • Monosaccharides with four, five, six, and seven carbon atoms
    • Colorless, crystalline solids that are freely soluble in water and insoluble in nonpolar solvents.
      • Most have a sweet taste.
    • Asymmetric carbon atoms (except dihydroxyacetone).
      • Glyceraldehyde has two different optical isomers
      • Aldohexoses, with 4 chiral centers have 2⁴ = 16 stereoisomers
    • D and L forms: Hydroxyl group configuration on the reference carbon in Fischer projection
    • Epimers: Two sugars that differ only in their configuration around one carbon atom;
      • Examples:
        • D-glucose and D-mannose(differs only at C-2)
        • D-glucose and D-galactose (differs at C-4)

    Formation of Cyclic Structures

    • Five or more carbon atoms in the back bone are predominantly cyclic structures
    • Carbonyl group forms a covalent bond with a hydroxyl group along the chain.
    • Formation of cyclic structures results from a general reaction between alcohols and aldehydes or ketones to form hemiacetals or hemiketals.

    Reactions of Monosaccharides

    • Two molecules of an alcohol can add to a carbonyl carbon producing a hemiacetal (aldose) or hemiketal (ketose).
    • If the hydroxyl and carbonyl groups are on the same molecule a five or six-membered ring forms.
    • The addition of a second alcohol molecule produces an acetal or ketal.
    • The resultant linkage is a glycosidic bond.
    • If the two molecules reacting together are monosaccharides, the acetal or ketal formed is a disaccharide.

    Anomers

    • Isomeric forms of monosaccharides that differ in their configuration about the hemiacetal or hemiketal carbon atom (anomeric carbon).
    • α- and β-D-glucopyranose are examples.

    Mutarotation

    • The process of conversion of a- to b- or vice-versa with changing the optical rotation.

    Reducing Sugars

    • Monosaccharides can be oxidized by relatively mild oxidizing agents
    • Carbonyl carbon is oxidized into a carboxyl group
    • Glucose and other sugars can reduce cupric ions

    Oligosaccharides

    • Short chains of monosaccharide units, joined by glycosidic bonds
    • Sucrose (table sugar)
    • Glycoconjugates.

    Polysaccharides

    • Sugar polymers containing 20+ units
    • Some are linear chains(e.g., Cellulose)
    • Some are branched chains(e.g., Glycogen)
    • Both glycogen and cellulose are formed by recurring units of D-glucose.

    Disaccharides

    • Consist of two monosaccharides covalently joined by an O-glycosidic bond

    • The hydroxyl group on one sugar molecule reacts with the anomeric carbon of another sugar molecule

    • Hydrolyzed easily by acid and readily

    • Examples:

      • Maltose (two D-glucose residues)
        • alpha-glycosidic linkage
      • Lactose (D-galactose and D-glucose residues)
      • Sucrose (glucose and fructose residues)
        • Nonreducing sugar

    • N-glycosyl bonds join the anomeric carbon of a sugar to a nitrogen atom in glycoproteins and nucleotides.

      • Formation of a glycosidic bond renders a sugar nonreducing

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    Description

    Explore the fundamental aspects of carbohydrates, including their structure, functions, and classifications. This quiz covers monosaccharides, oligosaccharides, and polysaccharides, as well as their roles in energy storage and cell structure. Test your knowledge on these essential organic molecules!

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