Questions and Answers
What is the primary amino acid found in every third position of collagen's triple helix structure?
Which types of collagen make up over 90% of the collagen found in the human body?
Which of the following statements about collagen is true?
What role do proline and hydroxyproline play in the structure of collagen?
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Collagen can be classified into different types. What distinguishes type IV collagen from types I, II, and III?
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Which amino acids most often occupy the positions represented by X and Y in the characteristic sequence of collagen?
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What type of proteins are collagen and elastin classified as?
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Which of the following is a characteristic of fibrous proteins?
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What is the main type of structural feature that proteoglycans share?
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Which glycosaminoglycans are predominantly found in cartilage proteoglycans?
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What type of bond forms between the xylose and serine in the GAGs-protein linkage?
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What is the characteristic shape of a proteoglycan molecule compared to a common object?
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What stabilizes the association between proteoglycan monomers and hyaluronic acid?
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How many GAG chains can be covalently attached to a single core protein in a proteoglycan monomer?
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Which statement is true regarding the formation of proteoglycan aggregates?
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What distinguishes GAG chains from the core protein in terms of size?
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What structural components are Glycosaminoglycans (GAGs) primarily composed of?
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How do the negatively charged groups in GAGs affect their behavior in solution?
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What role do GAGs play in the extracellular matrix (ECM)?
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Which of the following is commonly associated with GAGs?
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What property of GAGs contributes to their viscous and lubricating nature in mucous secretions?
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Which bodily tissues are known to contain Glycosaminoglycans?
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What functional aspect do carboxylic and sulfate groups impart to Glycosaminoglycans?
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What major percentage of Glycosaminoglycans is composed of carbohydrates?
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Study Notes
Maroteaux-Lamy Syndrome
- Deficiency in arylsulfatase B leads to the accumulation of dermatan sulfate, causing Maroteaux-Lamy syndrome (MPS VI).
Proteoglycans Overview
- Essential components of extracellular matrix (ECM) and cell surfaces, consisting of a core protein with covalent glycosaminoglycan (GAG) attachments.
- Structure resembles a bottle brush, with GAG chains extending from the core.
Structure of Proteoglycan Monomer
- Comprised of a core protein to which up to 100 GAG chains are covalently linked.
- Each GAG chain can contain up to 200 disaccharide units.
- Main GAGs in cartilage proteoglycans include chondroitin sulfate and keratan sulfate.
- Proteoglycans belong to gene families with shared structural features, such as the aggrecan family.
GAGs-Protein Linkage
- GAGs are covalently bonded to core proteins via trihexosides (galactose-galactose-xylose) connecting to serine residues.
- O-glycosidic bonds form between xylose and serine hydroxyl groups.
Aggregate Formation in Proteoglycans
- Multiple proteoglycan monomers associate with hyaluronic acid forming non-covalent aggregates.
- Ionic interactions stabilize the association, assisted by link proteins.
Glycosaminoglycans (GAGs) Characteristics
- Composed of repeating disaccharide units made of amino sugars and uronic acids.
- Amino sugars may be acetylated or sulfated, contributing to negative charges.
- Negative charges lead to molecular repulsion and water attraction, producing viscous solutions and gel-like matrices.
GAGs Functionality
- Comprise up to 95% carbohydrates, forming the ground substance of ECM.
- Hydrated GAGs support ECM flexibility, interacting with structural and adhesive proteins.
- Serve as molecular sieves, regulating material movement within the ECM.
- Contribute to the viscous properties of mucous secretions, previously referred to as mucopolysaccharides.
Fibrous Proteins Overview
- Have compact structures resulting from diverse protein folding (secondary, tertiary, quaternary).
- Notable examples: collagen and elastin; minor examples include fibronectin and laminin.
Collagen Properties
- Most abundant protein in the human body (25% total protein mass).
- Forms tough fibers resistant to shearing forces, prevalent in bone, tendon, and skin.
- Comprises 28 distinct types, with 90% being types I, II, III, and IV.
- Types I, II, and III are fibrillar; Type IV forms networks resulting in a three-dimensional mesh.
Collagen Structure
- Composed of three helical polypeptide alpha chains in a triple helix configuration.
- Characterized by a repeating glycine-rich sequence (Gly-X-Y), where X is usually proline and Y is predominantly hydroxyproline.
- Proline and hydroxyproline enhance the rigidity of the collagen helix due to their restricted rotation and bulk.
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Description
Explore the role of proteoglycans and their connection to Maroteaux–Lamy syndrome, which arises from a deficiency in arylsulfatase B. This quiz highlights the structure and importance of proteoglycans in the extracellular matrix and cell surfaces, as well as the clinical implications of their dysfunction.
