Biochemistry-2: Carbohydrate Chemistry
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Questions and Answers

What type of glycosidic linkages are present in cellulose?

  • α-(l ----> 4) glucosidic bonds
  • α-(1 ----> 6) glucosidic bonds
  • β-(l ------> 4) linkages (correct)
  • α-(l ----> 6) glucosidic bonds

    • What is the function of proteoglycans in the body?

  • Component of RNA
  • Component of ECM (correct)
  • Component of cell wall
  • Component of DNA

    • What is the term for carbohydrates linked to protein?

  • Glycolipid
  • Mucopolysaccharide
  • Glycoprotein (correct)
  • Proteoglycan

    • What are the repeating units of glycosaminoglycan (GAG) chains?

    <p>Disaccharide units</p> Signup and view all the answers

    What is the function of proteoglycans in the cell membrane?

    <p>Act as cell surface receptors for hormones</p> Signup and view all the answers

    What is the term for the carbohydrate part of proteoglycans?

    <p>Glycosaminoglycan (GAG)</p> Signup and view all the answers

    What is the function of proteoglycans in the GIT?

    <p>Component of mucins in the GIT</p> Signup and view all the answers

    What is a primary function of carbohydrates in living organisms?

    <p>Primary source of energy</p> Signup and view all the answers

    Which classification of carbohydrates includes glucose and fructose?

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

    What type of polymer is glycogen?

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

    Which of the following carbohydrates performs structural functions in plants?

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

    What distinguishes a heteroglycan from a homoglycan?

    <p>Type of monosaccharide units</p> Signup and view all the answers

    Which type of carbohydrate is sucrose classified under?

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

    Where is chondroitin sulphate commonly found?

    <p>Skin, blood vessels, heart valves &amp; cartilage</p> Signup and view all the answers

    What differentiates epimers from other sugar molecules?

    <p>They differ in configuration at only one of several chiral centers</p> Signup and view all the answers

    Why does dihydroxyacetone not have enantiomers?

    <p>It has no chiral center</p> Signup and view all the answers

    Which component is part of intracellular granules of mast cells?

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

    What is the smallest monosaccharide aldose?

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

    How many possible stereoisomers exist for a compound with $n$ chiral carbons?

    <p>$2^n$</p> Signup and view all the answers

    Which sulfate is typically found in the cornea?

    <p>Keratan sulphate</p> Signup and view all the answers

    How are D- and L- configurations of sugar molecules determined?

    <p>By the position of the -OH group on the bottommost stereo genic center</p> Signup and view all the answers

    What is the characteristic feature of an anomeric carbon in ring structures?

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

    In Haworth projections, groups below the plane of the ring correspond to what in Fischer projections?

    <p>Groups on the right-hand side</p> Signup and view all the answers

    Which entities are epimers in the context of monosaccharides?

    <p>Monosaccharides differing in the configuration around one carbon atom</p> Signup and view all the answers

    Which of the following monosaccharides is a reducing sugar?

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

    What distinguishes α and β anomers in carbohydrate structures?

    <p>The orientation of hydroxyl group on the anomeric carbon</p> Signup and view all the answers

    Which of the following sugars is non-reducing?

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

    How do the groups on the two ring carbons bonded to the endocyclic oxygen atom behave in Haworth projections?

    <p>They do not apply to the typical rules</p> Signup and view all the answers

    What describes D-glucose and L-glucose?

    <p>Optical isomers</p> Signup and view all the answers

    Why is sucrose considered a non-reducing sugar?

    <p>Because both anomeric carbons are involved in bonding</p> Signup and view all the answers

    Which carbon is typically the anomeric carbon for aldoses?

    <p>C-1</p> Signup and view all the answers

    What defines whether a sugar is a D- or L-sugar in a Fischer projection?

    <p>The position of the –OH group at the highest numbered asymmetric carbon</p> Signup and view all the answers

    Which carbon is the anomeric carbon in D-gulose?

    <p>C-1</p> Signup and view all the answers

    What type of stereoisomers are D-gulose and D-glucose?

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

    Why are some monosaccharides considered reducing sugars?

    <p>Because they contain free anomeric carbons</p> Signup and view all the answers

    How can one determine the alpha anomer in a Haworth projection?

    <p>By finding the –OH group pointing below the ring</p> Signup and view all the answers

    At what position is the OH group that determines the D- or L- configuration in D-gulose?

    <p>C-5</p> Signup and view all the answers

    Study Notes

    Carbohydrate Chemistry

    • Carbohydrates are polymers of monosaccharides (CH2O)n, acting as energy-storage molecules and structural components.
    • They are the main source of energy for living organisms and can be oxidized to yield energy to drive metabolic processes.

    Functions of Carbohydrates

    • Primary source of energy
    • Energy-storage molecules
    • Help reserve muscle
    • Structural functions (e.g., ribose in RNA, deoxyribose in DNA, cellulose in plant cell wall)

    Classification of Carbohydrates

    • Simple:
      • Monosaccharides (e.g., glucose, galactose, fructose)
      • Disaccharides (e.g., sucrose)
      • Oligosaccharides (2-20 units)
      • Polysaccharides (>20 units)
    • Glycoconjugates:
      • Linked covalently to a peptide chain, protein, or lipid

    Homoglycans and Heteroglycans

    • Homoglycan: polysaccharide containing only one type of monosaccharide unit (e.g., starch, glycogen)
    • Heteroglycan: polysaccharide containing more than one type of monosaccharide unit (e.g., lactose)

    Polysaccharides

    • Homoglycans:
      • Chondroitin sulfate (skin, blood vessels, heart valves, and cartilage)
      • Dermatan sulfate (cartilage, bone, heart valves)
      • Heparin and Heparan sulfates (basement membranes, components of cell surfaces)
      • Keratan sulfate (cornea, bone, cartilage aggregated with chondroitin sulfates)

    Stereoisomers, Epimers, and Enantiomers

    • Stereoisomers: compounds having the same structural formula but differing in spatial configuration
    • Epimers: sugar molecules that differ in configuration at only one of several chiral centers
    • Enantiomers: occur when you have 2 mirror image structures that aren't superimposable, with opposite configurations at each chiral carbon

    D- and L- Configurations of Sugars

    • Look at the –OH on the bottommost stereogenic center that is far away from the carbonyl group
    • If the OH- is on the right, then it's D-, while if it is on the left, then it's L-

    Anomers

    • The most oxidized carbon of a cyclized monosaccharide, the one attached to two oxygen atoms, is referred to as the anomeric carbon

    Conjugated Carbohydrates

    • Carbohydrates + protein or carbohydrates + lipid
    • Includes:
      • Glycolipid (in lipid part)
      • Glycoprotein (mucoproteins) and proteoglycan:
        • Both consist of protein + carbohydrates
        • Differ in sites, sugars, shape, and size

    Glycoprotein and Proteoglycan

    • Glycoprotein: protein part >> CHO part
    • Proteoglycan: consist of chains of GAGs attached to protein core (CHO >> protein part)
    • Functions:
      • Component of ECM and supporting tissues like cartilage
      • Component of mucins in GIT and lung
      • Component of cell membrane and acts as blood group antigen and cell surface receptors for hormones

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    Learn about the chemistry of carbohydrates, their role as energy-storage molecules, and their structural components in living organisms.

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