Carbohydrate Stereochemistry: Fischer Projection
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Questions and Answers

What type of ring does pyranose form?

  • Five-membered hemiacetal ring
  • Six-membered hemiacetal ring (correct)
  • Seven-membered hemiacetal ring
  • Four-membered hemiacetal ring

    • What is the characteristic of α anomer in a cyclic hemiacetal ring?

  • The -OH on the anomeric carbon is above the plane of the ring
  • The -OH on the anomeric carbon is on the side of the ring opposite from the terminal -CH2OH (correct)
  • The -OH on the anomeric carbon is on the same side of the ring as the terminal -CH2OH
  • The -OH on the anomeric carbon is below the plane of the ring

    • What type of ring is formed when aldehydes and ketones react with alcohols?

  • Six-membered cyclic hemiacetal
  • Four-membered cyclic hemiacetal
  • Five-membered cyclic hemiacetal (correct)
  • Seven-membered cyclic hemiacetal

    • What is the product called when the carbonyl group of a monosaccharide is reduced to an hydroxyl group?

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

    What is the prefix 'deoxy' short for?

    <p>Without oxygen</p> Signup and view all the answers

    What is the process called when α- and β-anomers equilibrate in aqueous solution?

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

    What is the approximate sweetness of sorbitol compared to sucrose?

    <p>60% as sweet as sucrose</p> Signup and view all the answers

    What is the name of the new carbon stereocenter created in forming the cyclic structure?

    <p>Anomeric carbon</p> Signup and view all the answers

    What is the product called when the aldehyde group of an aldose is oxidized under basic conditions?

    <p>Aldonic acid</p> Signup and view all the answers

    What is the orientation of the groups on carbons 1-5 of β-D-glucopyranose in Haworth projections and chair conformations?

    <p>Up, down, up, down, up</p> Signup and view all the answers

    What does the symbol 'β' indicate in carbohydrate chemistry?

    <p>The -OH on the anomeric carbon is on the same side of the ring as the terminal CH2OH</p> Signup and view all the answers

    What type of ring is D-glucose represented as in its most stable form?

    <p>Chair conformation ring</p> Signup and view all the answers

    What is the primary purpose of a Fischer projection?

    <p>To represent the configuration of tetrahedral stereocenters</p> Signup and view all the answers

    What is the general formula for a monosaccharide?

    <p>CnH2nOn</p> Signup and view all the answers

    What is the difference between an aldose and a ketose?

    <p>An aldose has an aldehyde group, while a ketose has a ketone group</p> Signup and view all the answers

    How are D-monosaccharides and L-monosaccharides differentiated?

    <p>By the position of the -OH on the penultimate carbon</p> Signup and view all the answers

    What is unique about the three amino sugars found in nature?

    <p>They all contain an -NH2 group in place of an -OH group</p> Signup and view all the answers

    What is the term for a monosaccharide that cannot be hydrolyzed to a simpler carbohydrate?

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

    What is the role of glucuronic acid in the body?

    <p>It is used to detoxify foreign phenols and alcohols</p> Signup and view all the answers

    What type of bond joins the two units of D-glucopyranose in maltose?

    <p>α-1,4-glycosidic bond</p> Signup and view all the answers

    What is the charge of a diphosphoric ester at the pH of cellular and intercellular fluids?

    <p>-2</p> Signup and view all the answers

    What is the difference between amylose and amylopectin?

    <p>Amylose is composed of unbranched chains, while amylopectin is branched</p> Signup and view all the answers

    What is sucrose?

    <p>A type of disaccharide</p> Signup and view all the answers

    What is the difference between reducing and non-reducing sugars?

    <p>Reducing sugars have an aldehyde or ketone group, while non-reducing sugars do not</p> Signup and view all the answers

    What is a characteristic common to most connective tissues?

    <p>They contain collagen and acidic polysaccharides</p> Signup and view all the answers

    What is the function of hyaluronic acid in the vitreous of the eye?

    <p>It maintains the retina in its proper position</p> Signup and view all the answers

    Why can humans not use cellulose as a source of glucose?

    <p>Because our digestive systems lack β-glucosidases</p> Signup and view all the answers

    What is the molecular weight range of heparin?

    <p>6000-30,000 g/mol</p> Signup and view all the answers

    Where is heparin synthesized and stored?

    <p>In mast cells of various tissues</p> Signup and view all the answers

    What is the best understood biological function of heparin?

    <p>Its anticoagulant activity</p> Signup and view all the answers

    Study Notes

    Carbohydrates and Their Structures

    • Anomeric Carbon: α formation means the -OH group is opposite to the terminal -CH2OH; β formation means it is on the same side.
    • Ring Structures: Pyranose indicates a six-membered hemiacetal ring, while furanose refers to a five-membered hemiacetal ring.
    • Aldopentoses: These also form cyclic hemiacetals due to their structure.

    Mutarotation

    • Definition: Mutarotation is the change in specific rotation during the equilibration of α- and β-anomers in solution.
    • Example: Dissolving either α-D-glucose or β-D-glucose in water leads to a specific rotation equilibrium of +52.7°, with compositions of 64% β and 36% α forms.

    Reduction to Alditols

    • Reduction Process: Monosaccharides can have their carbonyl group reduced to a hydroxyl group by agents like NaBH4 or H2 with a transition metal catalyst.
    • Alditols: Resulting from such reductions; common example: Sorbitol, found in fruits and used as a sugar substitute, is 60% as sweet as sucrose.

    Oxidation of Aldoses

    • Aldonic Acids: The aldehyde group in aldoses can be oxidized to form carboxylate anions under basic conditions.

    Cyclic Structures

    • Formation: Aldehydes and ketones react with alcohols to create hemiacetals, forming five- or six-membered rings.
    • D-Ribose: Predominantly occurs in the furanose form in nature.
    • D-Fructose: Forms a furanose cyclic structure as a 2-ketohexose.

    Haworth Projections and Chair Conformations

    • Cyclic Hemiacetals Representation: D-Glucose forms cyclic hemiacetals depicted in Haworth projections.
    • Chair Conformations: Provides a more accurate representation of pyranose structures, showing ring orientations and substituent positions.

    Anomers and Stereochemistry

    • Anomeric Carbon: C-1 for aldoses and C-2 for ketoses; stereoisomers differing at the anomeric carbon are termed anomers.
    • β-D-Glucopyranose: In its structure, the group orientations on carbons 1-5 are specified as up, down, up, down, and up.

    Carbohydrate Terminology

    • Carbohydrate Definition: Comprises polyhydroxyaldehydes or polyhydroxyketones, or compounds yielding them upon hydrolysis.
    • Monosaccharides: Simplest carbohydrates not reducible to simpler forms, following the general formula ( C_n(H_2O)_n ).
    • Classification: Based on the carbonyl group type; aldoses contain aldehyde groups, ketoses contained ketone groups.

    Amino Sugars

    • Characteristics: Contain an -NH2 group instead of -OH; include D-glucosamine, D-mannosamine, and D-galactosamine.
    • Biological Role: Amino sugars help detoxify compounds in the liver.

    Disaccharides and Polysaccharides

    • Polysaccharides: Composed of many monosaccharide units linked by glycosidic bonds; starch is a notable polymer of D-glucose consisting of amylose and amylopectin.
    • Maltose: A disaccharide made of two D-glucopyranose units linked by α-1,4-glycosidic bonds, classified as a reducing sugar.

    Connective Tissue and Hyaluronic Acid

    • Connective Tissue: Comprises various forms like cartilage and bone, primarily made of collagen and acidic polysaccharides, notably hyaluronic acid.
    • Hyaluronic Acid Functions: Abundant in embryonic tissues and synovial fluid, it maintains tissue elasticity and hydration.

    Cellulose and Heparin

    • Cellulose Structure: Linear polymer with up to 3000 units of D-glucose linked by β-1,4-glycosidic bonds; indigestible by humans due to lack of specific enzymes.
    • Heparin: A variable polysaccharide with anticoagulant properties, synthesized in mast cells, and has molecular weight ranging from 6,000 to 30,000 g/mol.

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    Description

    Test your understanding of carbohydrate stereochemistry and Fischer projections, a 2D representation of tetrahedral stereocenters. Learn about monosaccharides and how to interpret horizontal and vertical bonds.

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