Biochemistry Chapter 14: Glycosaminoglycans
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Questions and Answers

What is the main component of proteoglycans?

  • Protein
  • Lipid
  • Carbohydrate (correct)
  • Nucleic Acid

    • What is the function of GAGs in the body?

  • To transport oxygen
  • To provide structural support
  • To bind large amounts of water (correct)
  • To store energy

    • What is the difference between proteoglycans and glycoproteins?

  • Proteoglycans are found in the cytoplasm, glycoproteins are found in the ER
  • Proteoglycans have more protein, glycoproteins have more carbohydrate
  • Proteoglycans are found in the nucleus, glycoproteins are found in the mitochondria
  • Proteoglycans have more carbohydrate, glycoproteins have more protein (correct)

    • What is the role of fibrous structural proteins in the ECM?

    <p>To provide structural support</p> Signup and view all the answers

    What is the extracellular matrix (ECM) composed of?

    <p>Glycosaminoglycans, fibrous structural proteins, and adhesive proteins</p> Signup and view all the answers

    What is the main difference between glycosaminoglycans and proteoglycans?

    <p>Glycosaminoglycans are chains of sugars, proteoglycans are complexes of sugars and proteins</p> Signup and view all the answers

    What is the role of glycosaminoglycans in the ECM?

    <p>To bind large amounts of water</p> Signup and view all the answers

    What is the composition of a proteoglycan?

    <p>A large amount of carbohydrate and a small amount of protein</p> Signup and view all the answers

    What is the role of hydrated GAGs in the ECM?

    <p>To provide structural support and interact with proteins</p> Signup and view all the answers

    What is the main component of proteoglycans?

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

    How do proteoglycan monomers associate with hyaluronic acid?

    <p>Through ionic interactions</p> Signup and view all the answers

    What is the general structure of GAGs?

    <p>Unbranched heteropolysaccharide chains</p> Signup and view all the answers

    What is unique about keratan sulfate?

    <p>It contains galactose instead of an acidic sugar</p> Signup and view all the answers

    What is the primary function of link proteins?

    <p>To stabilize proteoglycan aggregates</p> Signup and view all the answers

    What is the main difference between proteoglycans and glycoproteins?

    <p>Proteoglycans have more carbohydrate than protein</p> Signup and view all the answers

    What is the term for the repeating unit of GAGs?

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

    What is the usual form of the amino group in glycosaminoglycans?

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

    What is the function of the sulfate groups in glycosaminoglycans?

    <p>To provide a negative charge</p> Signup and view all the answers

    What is the result of the negative charge of glycosaminoglycans in solution?

    <p>They repel each other</p> Signup and view all the answers

    What is the effect of compressing a solution of glycosaminoglycans?

    <p>The GAGs are forced to occupy a smaller volume</p> Signup and view all the answers

    What is the characteristic of mucous secretions and synovial fluid due to the presence of glycosaminoglycans?

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

    What is the epimer of D-glucuronic acid?

    <p>L-iduronic acid</p> Signup and view all the answers

    What is the main component of a proteoglycan monomer found in cartilage?

    <p>Core protein</p> Signup and view all the answers

    What is the type of bond that can occur on carbon 4 or 6 in glycosaminoglycans?

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

    How many disaccharide units are found in each GAG chain?

    <p>Up to 200</p> Signup and view all the answers

    What is the type of sugar that can be found in glycosaminoglycans?

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

    What is the type of bond formed between the xylose and the hydroxyl group of the serine?

    <p>O-glycosidic bond</p> Signup and view all the answers

    How are proteoglycan monomers associated with hyaluronic acid?

    <p>Through ionic interactions</p> Signup and view all the answers

    What is the structure of proteoglycan monomers resembles?

    <p>A brush</p> Signup and view all the answers

    What is the linkage between the carbohydrate chain and the protein?

    <p>Through a trihexoside</p> Signup and view all the answers

    What is the name of the integral membrane proteoglycan?

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

    What is the type of proteoglycans found primarily in the nervous system?

    <p>Neurocan and Cerebrocan</p> Signup and view all the answers

    What is the order of removal of groups during lysosomal degradation of GAGs?

    <p>The last group added during synthesis is the first group removed.</p> Signup and view all the answers

    What is the consequence of deficiencies in lysosomal enzymes involved in GAG degradation?

    <p>Accumulation of partially degraded carbohydrates.</p> Signup and view all the answers

    What is the prevalence of mucopolysaccharidoses?

    <p>1:25,000 live births.</p> Signup and view all the answers

    What is the characteristic of mucopolysaccharidoses?

    <p>Accumulation of glycosaminoglycans in various tissues.</p> Signup and view all the answers

    What is the result of incomplete lysosomal degradation of GAGs?

    <p>Presence of oligosaccharides in the urine.</p> Signup and view all the answers

    What is the cause of mucopolysaccharidoses?

    <p>Deficiency of any one of the lysosomal hydrolases.</p> Signup and view all the answers

    What is the effect of mucopolysaccharidoses on the body?

    <p>Skeletal and extracellular matrix deformities, and intellectual disability.</p> Signup and view all the answers

    What is the characteristic of progressive diseases?

    <p>The disease worsens over time.</p> Signup and view all the answers

    Study Notes

    Overview of Glycosaminoglycans

    • Glycosaminoglycans (GAGs) are large, negatively charged heteropolysaccharide chains associated with a small amount of protein ("core protein") to form proteoglycans.
    • Proteoglycans typically consist of up to 95% carbohydrate and 5% core protein.
    • GAGs have the ability to bind large amounts of water, producing a gel-like matrix that forms the basis of the body's ground substance.
    • The hydrated GAGs serve as a flexible support for the extracellular matrix (ECM), interacting with structural and adhesive proteins.

    Structure of Glycosaminoglycans

    • Proteoglycans are found in the ECM and on the outer surface of cells.
    • GAGs are associated with a small amount of protein ("core protein") by an O-glycosidic bond, forming proteoglycans.
    • Proteoglycans contain a greater amount of carbohydrate than do glycoproteins, which consist primarily of protein with a variable amount of carbohydrate.
    • GAGs are long, unbranched heteropolysaccharide chains composed of a repeating disaccharide unit ([acidic sugar–amino sugar]n).
    • Keratan sulfate is an exception, containing galactose instead of an acidic sugar.
    • The amino sugar is either D-glucosamine or D-galactosamine, which may be acetylated, sulfated, or non-acetylated.
    • The acidic sugar is either D-glucuronic acid or L-iduronic acid (C-5 epimer of D-glucuronic acid).

    Relationship between Glycosaminoglycan Structure and Function

    • Being negatively charged, GAG chains are extended in solution and repel each other, producing the "slippery" consistency of mucous secretions and synovial fluid.
    • When a solution of GAGs is compressed, the water is "squeezed out" and the GAGs are forced to occupy a smaller volume.

    Structure of Proteoglycan Monomers

    • A proteoglycan monomer found in cartilage consists of a core protein and up to 100 linear chains of GAGs covalently attached to the core protein.
    • Each GAG chain contains up to 200 disaccharide units.
    • The resulting structure resembles a "bottle brush".

    Degradation of Glycosaminoglycans

    • Lysosomal degradation of GAGs involves the removal of the last group added during synthesis, followed by the action of sulfatases or exoglycosidases.
    • Endo- and exoglycosidases are also involved in the lysosomal degradation of glycoproteins and glycolipids.
    • Deficiencies in these enzymes result in the accumulation of partially degraded carbohydrates, leading to tissue damage.

    Mucopolysaccharidoses

    • Mucopolysaccharidoses are hereditary diseases characterized by the accumulation of glycosaminoglycans in various tissues, causing progressive symptoms such as skeletal and extracellular matrix deformities, and mental retardation.
    • These diseases are caused by a deficiency of any one of the lysosomal hydrolases normally involved in the degradation of heparan sulfate and/or dermatan sulfate.
    • This results in the presence of oligosaccharides in the urine, due to incomplete lysosomal degradation of glycosaminoglycans.

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    Description

    This quiz covers the basics of glycosaminoglycans, proteoglycans, and glycoproteins. It is part of a biochemistry course, specifically chapter 14. Topics include the structure and function of glycosaminoglycans.

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