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Biochemistry: Fibrous Proteins
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Biochemistry: Fibrous Proteins

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@VeritableJadeite

Questions and Answers

What role does glycine play in the collagen structure?

  • It aids in the hydroxylation of proline.
  • It facilitates crosslinking of collagen fibers.
  • It is found in every third position of the polypeptide chain. (correct)
  • It contributes to the glycosylation process.

    • Which of the following elements is NOT required for the hydroxylation of proline and lysine in collagen biosynthesis?

  • Oxygen
  • Hydroxylating enzymes
  • Ferrous form of Iron
  • Hydrogen gas (correct)

    • What is the primary consequence of ascorbic acid deficiency in collagen synthesis?

  • Significant rise in hydroxyproline levels
  • Enhanced collagen crosslinking
  • Increased hydroxylation of lysine
  • Impaired interchain hydrogen bond formation (correct)

    • Which amino acid is primarily modified during glycosylation in collagen?

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

    What structure is characteristic of collagen?

    <p>Triple-helical with fibrous structure</p> Signup and view all the answers

    Which cell type is primarily responsible for collagen synthesis in cartilage?

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

    In collagen's repeating amino acid sequence, what does 'Y' typically represent?

    <p>Hydroxyproline or hydroxylysine</p> Signup and view all the answers

    Which enzyme is NOT involved in the hydroxylation of proline in collagen synthesis?

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

    How do specific amino acid sequences in prepro-α chains influence collagen biosynthesis?

    <p>They signal the polypeptide for secretion from the cell.</p> Signup and view all the answers

    What effect does hydroxyproline have on collagen structure?

    <p>Maximizes interchain H-bond formation</p> Signup and view all the answers

    What is the primary role of α1-antitrypsin in relation to elastin?

    <p>It inhibits the degradation of elastin.</p> Signup and view all the answers

    Which type of collagen is primarily involved in forming the basement membrane?

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

    What is the fundamental structural characteristic of collagen?

    <p>It consists of three polypeptides forming a helix.</p> Signup and view all the answers

    Which type of collagen is classified as a fibril-associated collagen?

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

    What type of collagen provides tensile strength and is abundant in tendons?

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

    What occurs as a consequence of α1-antitrypsin deficiency?

    <p>Emphysema due to elastin degradation.</p> Signup and view all the answers

    Which structure is defined as a semipermeable filtration barrier in the body?

    <p>Basement membrane composed of Type IV collagen</p> Signup and view all the answers

    What characterizes the packing of elastin molecules observed in an electron microscope?

    <p>Regular staggered packing</p> Signup and view all the answers

    Which of the following is NOT a feature of collagen?

    <p>Existing as a soluble protein in serum</p> Signup and view all the answers

    What type of collagen primarily forms a 3-dimensional mesh instead of fibrils?

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

    What is the primary structural feature that characterizes collagen?

    <p>Triple-helical structure</p> Signup and view all the answers

    Which type of collagen is known for its role in providing high tensile strength in tendons?

    <p>Type I</p> Signup and view all the answers

    Which amino acids are specifically modified to stabilize the collagen structure?

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

    What process involves the formation of pro-α chains in collagen biosynthesis?

    <p>Precursor synthesis</p> Signup and view all the answers

    What is the main classification criterion for the three groups of collagen?

    <p>Location and function in the body</p> Signup and view all the answers

    During collagen fibril formation, which step typically occurs last?

    <p>Extracellular cleavage of procollagen</p> Signup and view all the answers

    Which type of collagen primarily supports cartilaginous structures?

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

    What group do fibril-associated collagens belong to among the types of collagen?

    <p>They are a separate category</p> Signup and view all the answers

    What common outcome results from collagen degradation?

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

    What is the primary physiological role of α1-antitrypsin in relation to neutrophil elastase?

    <p>Inhibiting the activity of neutrophil elastase</p> Signup and view all the answers

    Where is α1-antitrypsin predominantly synthesized in the human body?

    <p>Liver and tissues such as monocytes</p> Signup and view all the answers

    Which of the following best describes the composition of alpha-keratins?

    <p>Rich in cysteine enabling disulfide bond formation</p> Signup and view all the answers

    What is a consequence of the activity of α1-antitrypsin on proteolytic enzymes?

    <p>Inhibition of hydrolytic enzyme activity</p> Signup and view all the answers

    What structure do alpha-keratins primarily contribute to in the human body?

    <p>Tough fibers in hair and nails</p> Signup and view all the answers

    What percentage of α1-antitrypsin comprises α1-globulin in the human body?

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

    What is the half-life of normal collagens?

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

    Which components are involved in the formation of procollagen?

    <p>Pro-α chains, hydroxylation, and glycosylation</p> Signup and view all the answers

    What process follows the cleavage of procollagen molecules?

    <p>Degradation into amino acids by proteinases</p> Signup and view all the answers

    What forms the interchain disulfide bonds during procollagen synthesis?

    <p>C-terminal of the pro-α chain</p> Signup and view all the answers

    Which enzyme is responsible for the breakdown of collagen?

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

    What part of procollagen is specifically cleaved by procollagen peptidases?

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

    What feature contributes to the stability of normal collagens?

    <p>Formation of procollagen molecules</p> Signup and view all the answers

    What type of collagen is specifically mentioned in relation to collagenases?

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

    What is the primary function of proteolytic enzymes regarding collagen?

    <p>Breakdown collagen</p> Signup and view all the answers

    Which fragment length is a product of procollagen cleavage?

    <p>3/4 + 1/4 length fragments</p> Signup and view all the answers

    Study Notes

    Collagen

    • Most abundant protein in the human body, characterized by a long, rigid structure formed by three polypeptide chains.
    • Types of collagen:
      • Fibril-forming collagens: Types I (skin, tendons), II (cartilage), III (reticular fibers).
      • Network-forming collagens: Types IV (basement membranes), VII (anchoring fibrils).
      • Fibril-associated collagens: Types IX and XII, which bind to fibrils.
    • Unique triple-helical structure composed of a repeating amino acid sequence rich in proline and glycine, enabling stability through hydrogen bonding.

    Biosynthesis of Collagen

    • Begins in fibroblasts, osteoblasts, and chondroblasts with formation of precursor pro-α chains.
    • Hydroxylation: Proline and lysine residues are hydroxylated by enzymes requiring Vitamin C, iron, and oxygen; crucial for stabilizing the collagen helix.
    • Glycosylation: Hydroxylysine undergoes enzymatic modification, typically with glucose or galactose.
    • Pro-α chains are assembled into procollagen, which is then cleaved outside the cell to form tropocollagen.

    Degradation of Collagen

    • Collagen is highly stable with a long half-life, undergoing constant remodeling via proteolytic enzymes, particularly collagenases from the metalloproteinase family.
    • Normal degradation is essential for tissue growth and repair, involving breakdown into amino acids.

    Collagenopathies

    • Ehlers-Danlos syndrome and osteogenesis imperfecta are disorders resulting from defects in collagen synthesis or structure.

    Elastin

    • Elastin provides elasticity to tissues like blood vessels and lungs, exhibiting a characteristic banding pattern under electron microscopy.
    • α1-antitrypsin protects elastin from degradation by inhibiting proteolytic enzymes, particularly in lung tissue, preventing conditions such as emphysema.

    α-Keratins

    • Found in hair, nails, and the outer layer of skin, forming tough, insoluble fibers.
    • Rich in cysteine, allowing for disulfide bonds which confer strength and resistance to stretching.

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    Description

    This quiz focuses on fibrous proteins, specifically collagen, and covers its different types, structure, and key amino acid sequences. Students will explore fibril-forming, network-forming, and fibril-associated collagens, along with the intricacies of collagen's triple-helical structure. Prepare to test your knowledge on these essential biochemistry concepts!

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