Protein Structure and Function
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Questions and Answers

What is the meaning of the term 'collagen' in Greek?

  • Fiber processor
  • Strength producer
  • Glue producer (correct)
  • Bone maker
  • What is the typical structure of collagen molecules?

  • A short, coiled structure
  • A long, flexible chain
  • A rope-like triple helix (correct)
  • A branched polymer
  • What percentage of the organic matrix of bone does collagen comprise?

  • 40%
  • 90% (correct)
  • 70%
  • 50%
  • Which amino acid is most abundant in collagen?

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

    How many polypeptide chains typically wind around each other in a collagen molecule?

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

    Which of the following tissues does NOT primarily contain collagen?

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

    What is a role of collagen in developing tissue?

    <p>Offering structural direction</p> Signup and view all the answers

    What type of fibers does collagen form that have high tensile strength?

    <p>Insoluble fibers</p> Signup and view all the answers

    What is the primary characteristic of secondary structure in proteins?

    <p>Local folding along short sections of the polypeptide chain</p> Signup and view all the answers

    Which type of interactions primarily determine the tertiary structure of a protein?

    <p>Hydrophobic interactions and disulfide bridges</p> Signup and view all the answers

    What defines the quaternary structure of a protein?

    <p>Multiple polypeptide chains joined together</p> Signup and view all the answers

    Which of the following is NOT a type of structural protein?

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

    How do hydrophobic interactions affect protein structure?

    <p>By promoting folding away from water</p> Signup and view all the answers

    What role do disulfide bridges play in protein structure?

    <p>They stabilize tertiary and quaternary structures</p> Signup and view all the answers

    Which type of bonding primarily occurs in the primary structure of a protein?

    <p>Peptide bonds</p> Signup and view all the answers

    Which of the following best describes the concept of 'whole molecule folding'?

    <p>It indicates the tertiary structure of a protein.</p> Signup and view all the answers

    Which amino acid is the precursor of hydroxylysine?

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

    What enzyme converts proline residues into hydroxyproline?

    <p>Prolyl hydroxylase</p> Signup and view all the answers

    What is required by prolyl hydroxylase to maintain its active state?

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

    Which sugars are commonly attached to hydroxylysine residues during glycosylation?

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

    What is the name of the larger precursors injected into the endoplasmic reticulum during collagen synthesis?

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

    Which type of collagen is primarily found in skin, tendon, bone, and cartilage?

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

    What forms when three pro-α chains combine?

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

    What type of enzyme is collagenase?

    <p>An enzyme that cleaves peptide bonds in collagen</p> Signup and view all the answers

    Which type of collagen is associated with the basement membrane?

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

    Which organism is known to secrete collagenase that causes gas gangrene?

    <p>Clostridium histolyticum</p> Signup and view all the answers

    What characteristic does glycine contribute to the collagen structure?

    <p>Enables packing in restricted spaces</p> Signup and view all the answers

    Which of the following is a characteristic of fibril-forming collagens?

    <p>They have a rope-like structure</p> Signup and view all the answers

    What is the primary structure of individual -keratin molecules in hair?

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

    What role does proline play in collagen synthesis?

    <p>Facilitates helical conformation</p> Signup and view all the answers

    How many protofibrils combine to form a microfibril in hair structure?

    <p>Eight protofibrils</p> Signup and view all the answers

    What are hydroxyproline and hydroxylysine derived from?

    <p>Hydroxylation of proline and lysine residues</p> Signup and view all the answers

    Which type of collagen is mainly found in cartilage and the vitreous humor?

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

    What structural unit is a bundle of hundreds of microfibrils referred to as?

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

    What aspect differentiates network-forming collagens from fibril-forming collagens?

    <p>Creation of a three-dimensional mesh</p> Signup and view all the answers

    What process is involved in creating a 'permanent wave' in human hair?

    <p>Reduction and rearrangement of disulfide bonds</p> Signup and view all the answers

    What introduces cross-links that harden -keratin in various tissues?

    <p>Disulfide cross-links</p> Signup and view all the answers

    What component is mixed with dead and living cells to create a complete strand of hair?

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

    Which of the following statements about structural proteins is true?

    <p>They are widely distributed in the body.</p> Signup and view all the answers

    Which characteristic describes the twisted cables of hardened hair?

    <p>They are stretchy and flexible.</p> Signup and view all the answers

    Study Notes

    Protein Structure

    • Secondary protein structure represents the initial folding of the primary structure along its chain. This "local folding" involves interactions between adjacent amino acids, specifically hydrogen bonds between R groups.
    • Tertiary protein structure is the three-dimensional folding of the secondary structure. This "whole molecule folding" is determined by interactions between R groups, including hydrophobic interactions, disulfide bridges, and hydrogen and ionic bonds.
    • Quaternary protein structure involves the joining of two or more polypeptide chains, which then become a functional protein. Hydrophobic interactions are the driving force for this level of protein structure.
    • The structure of proteins is influenced by the nature of the amino acid side chains, which can be either hydrophobic or hydrophilic and dictate how the protein folds to minimize energy and maximize stability.

    Structural Proteins

    • Structural proteins provide support to major structures such as bones, skin, cartilage, hair, and muscles.
    • Collagen, elastin, and keratin are examples of such proteins.

    Collagen

    • Collagen is the most abundant protein in mammals, making up about a quarter of total body weight.
    • It is a long, rigid molecule composed of three polypeptide chains (α chains) wound around each other in a triple helix.
    • Collagen serves as a major fibrous element in several tissues, including skin, bone, tendons, cartilage, blood vessels, and teeth.
    • The majority of the organic matrix of the bone is composed of collagen.
    • In addition to its structural role, collagen functions as a directive element in developing tissues.
    • Collagen fibers have high tensile strength.

    Collagen Structure

    • The most abundant protein in the body, comprised of a triple helix.
    • Each polypeptide chain contains approximately 1000 amino acids.
    • Glycine, proline, hydroxyproline, and lysine are the most abundant amino acids in collagen.

    Types of Collagen

    • There are various types of collagen with different compositions that give rise to structural components with slightly differing properties.
    • Type I collagen is found in skin, tendons, bone, and cartilage.
    • Type II collagen is found in cartilage and vitreous humor.
    • Type III collagen is found in fetal skin, the cardiovascular system, and lung vessels.
    • Type IV collagen is found in the basement membrane.

    Collagen Synthesis

    • Individual collagen polypeptide chains are synthesized on membrane-bound ribosomes and passed into the lumen of the endoplasmic reticulum (ER).
    • Precursors called pro-α chains are hydroxylated and glycosylated within the ER lumen.
    • These pro-α chains then associate to form procollagen, a triple-stranded helical molecule.

    Collagenases

    • Collagenases are enzymes that break down collagen by cleaving peptide bonds in its characteristic helical regions.
    • The collagenase secreted by Clostridium histolyticum is a potent collagenolytic enzyme that can split collagen at over 200 sites.

    ⍺-Keratins

    • ⍺-keratin molecules are composed of long sequences that are entirely ⍺-helical.
    • Pairs of these helices intertwine and further twist together to form a 4-molecule protofibril.
    • Eight protofibrils assemble into a microfibril, which is the basis of hair structure.
    • Microfibrils combine and are bound together with cells to create the final strand of hair.
    • The introduction of disulfide cross-links within the different levels of fiber structure hardens ⍺-keratin, making it stronger and more rigid.

    Summary

    • Structural proteins are widely distributed within the body, supporting various tissues.
    • Mutations in genes that control the synthesis of these proteins can lead to serious health issues.

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    Structural Proteins (PDF)

    Description

    This quiz explores the different levels of protein structure, including primary, secondary, tertiary, and quaternary forms. It focuses on the interactions and forces that dictate how proteins fold and achieve their functional shapes. Test your understanding of structural proteins and their significance in biological systems.

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