Questions and Answers
Which type of collagen is primarily associated with tendon and corneal structures?
What characterizes a triple-helical structure in collagen?
What role do hydroxyproline and hydroxylysine play in collagen?
Glycosylation in collagen biosynthesis is important for what reason?
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How many types of collagen are known to exist?
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What is the main function of fibril-associated collagens?
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What is the primary structure of collagen defined by?
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Which types of collagen are classified as fibril-forming collagens?
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Degradation of collagen is generally associated with which physiological processes?
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What is the significance of the half-life of normal collagens?
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What initiates the formation of procollagen from pro-α chains?
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Which enzymes are primarily responsible for the initial breakdown of procollagen?
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What is the outcome of the extracellular cleavage of procollagen?
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Which part of the procollagen molecule is flanked by nonhelical amino acids?
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Which family of proteins is involved in the further degradation of collagen into amino acids?
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What are the resulting fragments after the cleavage of procollagen?
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What role do propeptides play in the structure of procollagen?
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What type of collagen can be specifically degraded by collagenases as mentioned in the content?
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How does the collagen structure respond to tissue growth or injury?
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What is the primary physiological role of α1-antitrypsin in the body?
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Which enzyme's activity is inhibited by α1-antitrypsin?
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Where is α1-antitrypsin primarily synthesized?
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What characteristic makes alpha-keratins important in forming tough fibers?
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What structural role do alpha-keratins play in the body?
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What is a key feature of α1-antitrypsin that contributes to its function in proteolytic inhibition?
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What is the role of glycine in the structure of collagen?
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Which amino acids can undergo hydroxylation during collagen biosynthesis?
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What is required for the hydroxylation of proline and lysine in collagen?
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The repeating sequence found in collagen is denoted as Gly – X – Y. What does 'X' represent?
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What is the consequence of ascorbic acid deficiency in collagen synthesis?
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In collagen, what effect does glycosylation of hydroxylysine have?
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Which cells are primarily responsible for the synthesis of collagen precursors?
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How does hydroxyproline contribute to collagen's structure?
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What specific modification occurs to prepro-α chains during collagen synthesis?
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Collagen's triple-helical structure is primarily characterized by which of the following features?
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What is the role of lysyl oxidase in collagen formation?
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Which type of Ehlers-Danlos syndrome is most clinically important due to its impact on blood vessels?
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What is a characteristic symptom of Osteogenesis Imperfecta Type II?
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What mutation is associated with Osteogenesis Imperfecta Type I?
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Which of the following is NOT a characteristic feature of Ehlers-Danlos syndrome?
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What is the primary defect in Menkes disease?
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Which cross-linking enzyme requires copper as a cofactor?
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Which collagen type is primarily affected in Ehlers-Danlos syndrome?
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What is a common complication observed in individuals with Osteogenesis Imperfecta?
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Which of the following results from the mutation of the amino acid sequence in collagen types I, III, or V?
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Study Notes
Collagen
- Over 25 types of collagen identified, categorized into three main groups based on structure and function.
- Fibril-forming collagens (Types I, II, III) provide high tensile strength, forming supportive structures such as tendons and corneas.
- Network-forming and fibril-associated collagens serve different structural purposes in connective tissues.
Structure of Collagen
- Amino acid sequence rich in proline and glycine; repeating pattern of Gly-X-Y, where X is often proline and Y is hydroxyproline or hydroxylysine.
- Triple-helical structure formed by three polypeptide α-chains, contributing to collagen's fibrous and elongated shape.
- Hydroxyproline stabilizes the triple helix through interchain hydrogen bonds; not commonly found in other proteins.
Biosynthesis of Collagen
- Pro-α chains are synthesized in fibroblasts, osteoblasts, and chondroblasts and begin with an N-terminal signal sequence.
- Hydroxylation of proline and lysine is essential for stability, requiring enzymes, oxygen, iron, and vitamin C.
- Pro-α chains form procollagen which moves to the Golgi, where it is packaged and secreted.
- Extracellular cleavage by procollagen peptidases converts procollagen to tropocollagen, leading to fibril formation.
Collagen Degradation
- Collagen is highly stable with a long half-life, constantly remodeled by collagenases (metalloproteinases) in response to tissue growth or injury.
- Specific cleavage points lead to tropocollagen fragments, which are further degraded by proteinases.
Collagen Diseases (Collagenopathies)
- Ehlers-Danlos syndrome: Hereditary defect leading to a generalized connective tissue disorder affecting Types I, III, or V collagen. Symptoms include fragile skin and easy joint dislocations.
- Osteogenesis Imperfecta: Brittle bone syndrome causing fractures with minimal trauma. Two main types:
- Type I: Less severe, presenting in infancy with decreased collagen production.
- Type II: Most severe and fatal in utero or neonatally due to mutations in collagen genes.
α1-Antitrypsin and Elastin Degradation
- α1-antitrypsin (A1AT) acts as a protease inhibitor, particularly for neutrophil elastase that degrades elastin and other structural proteins.
- Predominantly synthesized in the liver, crucial for preventing tissue injury by controlling enzymatic activity in various tissues.
Alpha-Keratins
- Tough fibrous proteins found in hair, nails, and the outer layer of the epidermis.
- Constituent of intermediate filaments, distinguished by high cysteine content, providing disulfide bonds that enhance their insolubility and resistance to stretching.
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Description
Dive into the fascinating world of fibrous proteins with a focus on collagen. This quiz covers various types of collagen, including their structures and amino acid sequences, essential for understanding protein biology. Enhance your knowledge about collagen's unique triple-helical structure and its significance in biochemistry.