Proteoglycans and Their Functions
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Questions and Answers

Which proteoglycan is primarily synthesized by arterial smooth muscle cells?

  • Dermatan sulfate (correct)
  • Hyaluronic acid
  • Chondroitin sulfate
  • Heparan sulfate

    • What is the main organic component of bone material?

  • Type I collagen (correct)
  • Hyaluronic acid
  • Bone mineralization enzymes
  • Dermatan sulfate

    • Which component is predominantly found in the inorganic part of bone?

  • Gelatin
  • Crystalline hydroxyapatite (correct)
  • Type II collagen
  • Collagen type V

    • Which type of collagen is a minor component of bone?

    <p>Type V collagen</p> Signup and view all the answers

    In what way could proteoglycans contribute to the features of arthritis?

    <p>By serving as autoantigens</p> Signup and view all the answers

    Which of the following is not found among the principal proteins in bone?

    <p>Type II collagen</p> Signup and view all the answers

    What is the role of the noncollagen proteins in bone?

    <p>They assist in the mineralization process.</p> Signup and view all the answers

    What percentage of total bone protein is comprised of collagen type I?

    <p>Approximately 90%</p> Signup and view all the answers

    What is the primary type of collagen found in hyaline cartilage?

    <p>Collagen type II</p> Signup and view all the answers

    Which protein is involved in the attachment of type II collagen to chondrocytes?

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

    What type of proteins are COMP and aggrecan classified as in cartilage?

    <p>Noncollagen proteins</p> Signup and view all the answers

    What role do proteases, such as collagenases, play in cartilage?

    <p>Degrade collagen and other proteins</p> Signup and view all the answers

    Which of the following is the major proteoglycan of cartilage?

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

    How does cartilage primarily obtain its nutrients?

    <p>Synovial fluid</p> Signup and view all the answers

    Which factors are known to stimulate the production of proteases in cartilage?

    <p>Interleukin-1 and tumor necrosis factor α</p> Signup and view all the answers

    Which of these collagens helps control the diameter of type II collagen fibrils?

    <p>Collagen type XI</p> Signup and view all the answers

    What is one of the structural features typical of heparin?

    <p>Includes glucosamine and either D-glucuronic or L-iduronic acid</p> Signup and view all the answers

    Which component may be present in heparin's structure aside from glucosamine?

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

    What role does heparin primarily play in cell biology?

    <p>Cell growth mediator and communication facilitator</p> Signup and view all the answers

    What characteristic of heparin's turnover is mentioned?

    <p>Relatively slow turnover with half-lives of days to weeks</p> Signup and view all the answers

    Which of the following describes a potential modification of glucosamine in heparin?

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

    What type of residues may additionally occur in heparin's structure?

    <p>Non-sulfated or 3-O-sulfated glucosamine residues</p> Signup and view all the answers

    How does cell attachment to the substratum in culture occur?

    <p>Primarily mediated by heparan sulfate</p> Signup and view all the answers

    Which function is not associated with heparin based on the information provided?

    <p>Energy storage</p> Signup and view all the answers

    What is the primary cause of achondroplasia?

    <p>Mutations in the gene encoding fibroblast growth factor receptor 3 (FGFR3)</p> Signup and view all the answers

    Which protein is most abundant in the animal kingdom?

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

    Which of the following skeletal abnormalities is associated with affected individuals of achondroplasia?

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

    What type of inheritance pattern is commonly associated with achondroplasia?

    <p>Autosomal dominant</p> Signup and view all the answers

    Which of the following processes is NOT part of collagen biosynthesis?

    <p>Replication of DNA</p> Signup and view all the answers

    Which disease is NOT associated with impaired synthesis of collagen?

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

    Which type of proteins affect the growth and differentiation of mesenchymal and neuroectodermal cells?

    <p>Fibroblast growth factors</p> Signup and view all the answers

    What characteristic does elastin provide to tissues?

    <p>Extensibility and elastic recoil</p> Signup and view all the answers

    What is the primary consequence of the mutation in the gene encoding elastin?

    <p>Substitution of arginine for glycine</p> Signup and view all the answers

    Which of the following mutations is linked to Marfan syndrome?

    <p>Mutation in the gene encoding fibrillin-1</p> Signup and view all the answers

    Which of the following is NOT a characteristic of elastin?

    <p>Contains hydroxylysine</p> Signup and view all the answers

    What role does TGF-β play in the context of skeletal dysplasias?

    <p>Contributes to cardiovascular pathology</p> Signup and view all the answers

    Which of the following describes the structure of glycosaminoglycans (GAGs)?

    <p>Made of repeating disaccharides with uronic acids and hexosamines</p> Signup and view all the answers

    Which of the following is a major glycosaminoglycan?

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

    What is the function of lysosomal hydrolases in relation to GAGs?

    <p>Degrade GAGs sequentially</p> Signup and view all the answers

    Which skeletal dysplasia is associated with a mutation in a sulfate transporter?

    <p>Diastrophic dysplasia</p> Signup and view all the answers

    Study Notes

    Heparin as Receptors

    • Heparin can act as receptors for cells.
    • Heparin influences C cell growth and cell-cell communication.

    Heparan Sulfate

    • Heparan sulfate is involved in the attachment of cells to their substratum in cultures.

    Arterial Walls

    • The arterial walls contain hyaluronic acid, chondroitin sulfate, dermatan sulfate, and heparan sulfate proteoglycans.
    • Dermatan sulfate binds plasma low-density lipoproteins.
    • Dermatan sulfate is the major GAG synthesized by arterial smooth muscle cells.
    • Dermatan sulfate may be involved in the development of atherosclerotic plaques.

    Proteoglycans in Arthritis

    • Proteoglycans can act as autoantigens in various types of arthritis, contributing to the disease's pathological features.

    Bone Composition

    • Bone contains both organic and inorganic matter.
    • Organic matter is mainly protein, primarily collagen type I (90-95% of organic material) with smaller amounts of type V collagen and non-collagen proteins.
    • Inorganic matter primarily consists of crystalline hydroxyapatite (Ca10(PO4)6(OH)2).

    Key Proteins in Bone

    • Collagen type 1: Found in bone, composed of two alpha1(I) and one alpha2(I) chains.
    • Collagen type V: Minor component found in bone.
    • CS-PG I (biglycan): Contains two GAG Chains, found in other tissues.
    • CS-PG II (decorin): Contains one GAG Chain, found in other tissues.

    Cartilage Composition

    • Cartilage is composed of collagen (mainly type II) and non-collagen proteins.
    • Collagen type II is found in 90-98% of hyaline cartilage and is composed of three alpha1(II) chains.
    • Collagen types V, VI, IX, X, XI, and chondronectin are also present in cartilage.

    Key Proteins In Cartilage

    • Collagen type II: Found in 90-98% of hyaline cartilage, composed of three alpha1(II) chains.
    • Collagen type IX: Cross-links to collagen type II.
    • Collagen type XI: Helps control the diameter of type II fibrils.
    • Chondronectin: A protein involved in the attachment of type II collagen to chondrocytes.
    • Aggrecan: The major proteoglycan of cartilage.
    • DS-PG I (biglycan): Similar to CS-PG I of bone.
    • DS-PG II (decorin): Similar to CS-PG II of bone.

    Cartilage Characteristics

    • Cartilage is avascular and obtains most of its nutrients from synovial fluid.
    • Cartilage exhibits slow but continuous turnover.
    • Chondrocytes synthesize enzymes (collagenases and stromelysins) degrading collagen and other proteins in cartilage.
    • Interleukin-1 (IL-1) and tumor necrosis factor α (TNF-α) stimulate the degradation of cartilage.

    Achondroplasia

    • Individuals with achondroplasia have short limbs, normal trunk size, macrocephaly, and various skeletal abnormalities.
    • Achondroplasia is often inherited as an autosomal dominant trait, but new mutations can cause it.
    • This condition is not a collagen disorder but is due to mutations in the fibroblast growth factor receptor 3 (FGFR3) gene.
    • Mutations in FGFR3 typically involve nucleotide 1138, substituting arginine for glycine (residue number 380) in the transmembrane domain, rendering the protein inactive.

    Other Skeletal Dysplasias

    • Mutations in the FGFR3 gene can also lead to hypochondroplasia, thanatophoric dysplasia (types I and II), and the SADDAN phenotype (severe achondroplasia with developmental delay and acanthosis nigricans)).
    • Other skeletal dysplasias including craniosynostosis syndromes are also due to mutations in genes encoding FGF receptors.
    • Diastrophic dysplasia is caused by mutations in a sulfate transporter.

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    Description

    This quiz explores the roles and functions of proteoglycans, including their impact on cell growth, attachment in cultures, and involvement in arterial health and arthritis. Understand the significance of heparan sulfate and dermatan sulfate in various biological contexts.

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