Cyclic Forms of Monosaccharides and Enantiomers
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Questions and Answers

What defines a dextrorotatory compound?

  • A compound that rotates light counterclockwise
  • A chiral compound that rotates light clockwise (correct)
  • A compound that has no optical activity
  • A compound that does not rotate light

    • Which of the following statements about enantiomers is true?

  • Enantiomers can have significantly different biological effects. (correct)
  • Enantiomers have the same interactions with all chiral molecules.
  • Enantiomers react similarly with achiral solvents.
  • Enantiomers can have different boiling points but the same melting points.

    • How do enantiomers differ in terms of solubility?

  • Enantiomers have the same solubility in chiral solvents.
  • Enantiomers have different solubility in all solvents.
  • Enantiomers have the same solubility in achiral solvents. (correct)
  • Enantiomers have different solubility only in polar solvents.

    • Which factor does not affect the boiling point, melting point, or density of enantiomers?

    <p>Chirality of the compounds</p> Signup and view all the answers

    What is the relationship between + and - designations and D and L designations?

    <p>There is no correlation between D, L and +, - designations.</p> Signup and view all the answers

    What distinguishes the α-form of D-Glucose from the β-form?

    <p>The position of the –OH group on C1 relative to CH2OH on C5</p> Signup and view all the answers

    What would happen if two chiral molecules were to interact with each other?

    <p>They would have different reaction efficiencies due to their chirality.</p> Signup and view all the answers

    What are anomers?

    <p>Cyclic monosaccharides that differ in the position of the –OH on one of the carbon atoms</p> Signup and view all the answers

    Which statement about the rotational properties of enantiomers is accurate?

    <p>One enantiomer rotates light clockwise and the other counterclockwise.</p> Signup and view all the answers

    Which of the following monosaccharides is likely to form cyclic structures similar to D-Glucose?

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

    In what way could the body respond differently to enantiomers?

    <p>One enantiomer may enhance activity while the other is completely inactive.</p> Signup and view all the answers

    What is the difference between pyranose and furanose?

    <p>Pyranose contains a six-atom ring, while furanose contains a five-atom ring</p> Signup and view all the answers

    Which statement is true regarding the cyclic forms of monosaccharides?

    <p>Aldoses with five or more carbon atoms can establish equilibria</p> Signup and view all the answers

    What aspect of cyclic monosaccharides varies among aldoses with five or more carbon atoms?

    <p>Equilibrium percentages of the alpha, beta, and open-chain forms</p> Signup and view all the answers

    Which property is characteristic of glucose's cyclic forms?

    <p>They can interconvert between forms</p> Signup and view all the answers

    Why are cyclic forms of monosaccharides important in biochemistry?

    <p>They determine the metabolic pathways of carbohydrates</p> Signup and view all the answers

    What is a defining characteristic of enantiomers?

    <p>They are mirror images of each other.</p> Signup and view all the answers

    Which monosaccharide classification corresponds to a sugar with six carbon atoms and one aldehyde group?

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

    Which of the following is NOT a property of diastereomers?

    <p>They are mirror images of each other.</p> Signup and view all the answers

    What is the common name for D-Glucose?

    <p>Blood sugar</p> Signup and view all the answers

    What results from the replacement of a hydroxyl group with an amino group in a monosaccharide?

    <p>Amino sugar</p> Signup and view all the answers

    Which of the following typically has the highest percentage of glucose by mass?

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

    Which hydroxyl group is typically replaced by an amino group in naturally occurring amino sugars?

    <p>C2</p> Signup and view all the answers

    Which of the following best describes a ketopentose?

    <p>Monosaccharide with five carbon atoms and one ketone group.</p> Signup and view all the answers

    Which of these is a type of sugar produced from grape and ripe fruits that is significant for human nutrition?

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

    What type of linkage is formed between two monosaccharides in a disaccharide?

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

    Which two monosaccharides create maltose?

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

    What distinguishes aldoses from ketoses?

    <p>The presence of an aldehyde or ketone group.</p> Signup and view all the answers

    What type of glycosidic linkage is found in maltose?

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

    Why is maltose easily digested by humans?

    <p>An enzyme can break the α(1🡪4) linkages.</p> Signup and view all the answers

    Which statement correctly describes the formation of disaccharides?

    <p>One monosaccharide acts as a hemiacetal and the other as an alcohol.</p> Signup and view all the answers

    Which of the following is NOT derived from amino sugars?

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

    What is the primary function of cellulose in the diet?

    <p>To serve as dietary fiber and aid in digestion</p> Signup and view all the answers

    What type of glycosidic linkages are present in chitin?

    <p>β(1🡪4)</p> Signup and view all the answers

    Which of the following is an example of an acidic polysaccharide?

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

    What is the role of hyaluronic acid in the body?

    <p>To provide lubrication in joints</p> Signup and view all the answers

    What distinguishes acidic polysaccharides from other polysaccharides?

    <p>They have repeating disaccharide units with a negative charge</p> Signup and view all the answers

    Which of the following best describes the structural similarity between cellulose and chitin?

    <p>Both are linear polymers with β glycosidic linkages</p> Signup and view all the answers

    What type of sugar is involved in the composition of heparin?

    <p>N-acetyl-D-glucosamine</p> Signup and view all the answers

    How many disaccharide residues can be found in a chain of heparin?

    <p>15–90</p> Signup and view all the answers

    Study Notes

    Cyclic Forms of Monosaccharides

    • D-Glucose has two forms: α-form and β-form.
    • The α-form has the –OH group of carbon 1 and the CH2OH group of carbon 5 on opposite sides.
    • The β-form has the –OH group of carbon 1 and the CH2OH group of carbon 5 on the same side.
    • Anomers are cyclic monosaccharides that differ only in the position of the substituents on the anomeric carbon atom.
    • Aldoses with 5 or more carbon atoms establish similar equilibria like D-glucose, but with different percentages of alpha, beta, and open-chain forms.
    • Fructose and other ketoses with sufficient carbon atoms also cyclize.
    • Pyranose is a cyclic monosaccharide containing a six-atom ring.
    • Furanose is a cyclic monosaccharide containing a five-atom ring.

    Properties of Enantiomers

    • Enantiomers are optically active.
    • Dextrorotatory compounds rotate the plane of polarized light clockwise.
    • Levorotatory compounds rotate the plane of polarized light counterclockwise.
    • There is no correlation between D, L, and +, -.
    • Enantiomers react differently with other chiral molecules.
    • Enantiomers have the same solubility in achiral solvents but different solubility in chiral solvents.
    • Enantiomers have the same boiling points, melting points, and densities.
    • Diastereoisomers have different physical and chemical properties, while enantiomers have the same physical and chemical properties.

    Classification of Monosaccharides

    • Monosaccharides are classified based on the number of carbon atoms and functional groups.
    • Triose has 3 carbons, tetrose has 4 carbons, pentoses have 5 carbons, and hexoses have 6 carbons.
    • Aldoses have one aldehyde group.
    • Ketoses have one ketone group.

    Biochemically Important Monosaccharides

    • Glucose is the most abundant monosaccharide in nature.
    • Glucose is the most important source of human nutrition.
    • Glucose is also known as grape sugar or dextrose.
    • Blood sugar levels range from 70–100 mg/dL.

    Reactions of Monosaccharides

    • Amino sugars are formed when one of the hydroxyl groups of a monosaccharide is replaced with an amino group.
    • The C2 hydroxyl group is replaced by an amino group in naturally occurring amino sugars.
    • Amino sugars are important building blocks of polysaccharides such as chitin and hyaluronic acid.

    Disaccharides

    • Two monosaccharides can react to form a disaccharide.
    • The ether bond formed is a glycosidic linkage.
    • Maltose (malt sugar) is composed of two D-glucose units linked via an α(1→4) glycosidic linkage.
    • Humans can digest maltose easily because of an enzyme that can break α(1→4) linkages.

    Structural Polysaccharides

    • Cellulose is a linear polymer of D-glucose units linked via β(1→4) glycosidic linkages.
    • Cellulose is found in plant cell walls and is important for structural support.
    • Chitin is a linear polymer with all β(1→4) glycosidic linkages.
    • Chitin has an N-acetyl amino derivative of glucose.
    • Chitin gives rigidity to the exoskeletons of arthropods such as crabs, lobsters, shrimp, and insects.

    Acidic Polysaccharides

    • Acidic polysaccharides are polysaccharides containing a repeating disaccharide unit with an amino sugar and a sugar with a negative charge due to a sulfate or carboxyl group.
    • Acidic polysaccharides are heteropolysaccharides, meaning they contain different monosaccharides in an alternating pattern.
    • Hyaluronic acid is a highly viscous acidic polysaccharide that acts as a lubricant in joints and the vitreous humor of the eye.
    • Heparin is an acidic polysaccharide that acts as a blood anticoagulant.

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    Description

    Explore the distinct cyclic forms of monosaccharides such as D-Glucose and the properties of enantiomers, including their optical activity. This quiz delves into the structural characteristics and behavior of aldoses and ketoses, along with an overview of pyranose and furanose forms.

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