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Questions and Answers
Which of the following roles is NOT associated with the extracellular matrix (ECM)?
Which of the following roles is NOT associated with the extracellular matrix (ECM)?
What is the significance of the basement membrane in epithelial tissues?
What is the significance of the basement membrane in epithelial tissues?
How does the deletion of the extracellular matrix impact cellular activity?
How does the deletion of the extracellular matrix impact cellular activity?
Which condition is associated with damage to the glycocalyx?
Which condition is associated with damage to the glycocalyx?
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What is the primary component of the basement membrane?
What is the primary component of the basement membrane?
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Which of the following statements about the roles of endothelial cells is incorrect?
Which of the following statements about the roles of endothelial cells is incorrect?
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What role does the basement membrane play in relation to endothelial cells?
What role does the basement membrane play in relation to endothelial cells?
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In what way does the extracellular matrix contribute to tissue dynamics?
In what way does the extracellular matrix contribute to tissue dynamics?
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What role do proteoglycans primarily play in cell migration?
What role do proteoglycans primarily play in cell migration?
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Which of the following describes the structure of proteoglycans?
Which of the following describes the structure of proteoglycans?
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What is a significant function of matrix metalloproteinases (MMPs)?
What is a significant function of matrix metalloproteinases (MMPs)?
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How do integrins contribute to cellular interaction with the extracellular matrix?
How do integrins contribute to cellular interaction with the extracellular matrix?
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What process is crucial for the remodeling of the extracellular matrix?
What process is crucial for the remodeling of the extracellular matrix?
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What primary structural role does collagen play within the extracellular matrix?
What primary structural role does collagen play within the extracellular matrix?
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Which type of collagen is primarily involved in the formation of the basement membrane?
Which type of collagen is primarily involved in the formation of the basement membrane?
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What is the primary consequence of a deficiency in vitamin C regarding collagen?
What is the primary consequence of a deficiency in vitamin C regarding collagen?
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Goodpasture’s syndrome is characterized by which of the following?
Goodpasture’s syndrome is characterized by which of the following?
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Which characteristic is true regarding fibrillar collagens?
Which characteristic is true regarding fibrillar collagens?
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Which genetic mutation is associated with collagen type I?
Which genetic mutation is associated with collagen type I?
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The mechanical properties of skin and tendons primarily depend on which type of collagen?
The mechanical properties of skin and tendons primarily depend on which type of collagen?
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Which condition is linked to collagen type III mutations?
Which condition is linked to collagen type III mutations?
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How does thin basement membrane disease primarily affect kidney function?
How does thin basement membrane disease primarily affect kidney function?
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What is a common outcome of vitamin C deficiency related to collagen health?
What is a common outcome of vitamin C deficiency related to collagen health?
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What is the primary function of tight junctions in cell-cell interactions?
What is the primary function of tight junctions in cell-cell interactions?
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Which junction connects actin filaments between cells?
Which junction connects actin filaments between cells?
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What do hemidesmosomes primarily anchor to?
What do hemidesmosomes primarily anchor to?
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What component primarily mediates cell-cell and cell-substratum interactions?
What component primarily mediates cell-cell and cell-substratum interactions?
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What type of junction allows the passage of small water-soluble molecules?
What type of junction allows the passage of small water-soluble molecules?
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Which of the following types of junctions are characterized by connections of intermediate filaments?
Which of the following types of junctions are characterized by connections of intermediate filaments?
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Which structure is primarily found at the basal surface of epithelial cells?
Which structure is primarily found at the basal surface of epithelial cells?
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Which of the following best describes focal adhesions?
Which of the following best describes focal adhesions?
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What is the composition of the glycocalyx?
What is the composition of the glycocalyx?
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What type of junction is least likely to be found in connective tissue?
What type of junction is least likely to be found in connective tissue?
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What is the role of the tunica intima in blood vessels?
What is the role of the tunica intima in blood vessels?
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Which layer of blood vessels contains elastic fibers?
Which layer of blood vessels contains elastic fibers?
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What is NOT a function of the endothelial layer of the tunica intima?
What is NOT a function of the endothelial layer of the tunica intima?
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Which statement accurately describes the tunica adventitia?
Which statement accurately describes the tunica adventitia?
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Cell-cell and cell-ECM interactions are crucial for which of the following?
Cell-cell and cell-ECM interactions are crucial for which of the following?
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What primarily distinguishes the tunica media from the other layers of blood vessels?
What primarily distinguishes the tunica media from the other layers of blood vessels?
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Which layer of the blood vessel is primarily involved in controlling blood flow?
Which layer of the blood vessel is primarily involved in controlling blood flow?
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The basal lamina is a component of which structure?
The basal lamina is a component of which structure?
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What keeps endothelial and epithelial cells together?
What keeps endothelial and epithelial cells together?
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Study Notes
Endothelium
- A protective lining on all blood vessels.
- Acts as a barrier to molecules.
- Binds regulatory factors.
- Adsorbs nutrients.
- Provides an environment for enzymes.
Glycocalyx
- A cell coat of glycoproteins and glycolipids that project outward from the plasma membrane.
- Located at epithelial and endothelial cells.
- Mediates cell-cell and cell-substratum interactions.
- Provides mechanical protection for cells.
- Important for primordial germ cell migration.
Extracellular Matrix (ECM)
- An organized network of extracellular material.
- Provides physical and biochemical signals.
- Regulates the shape and activities of tissues.
- Its removal alters cellular synthetic and secretory activity.
- A dynamic structure that is degraded and reformed.
Basement Membrane (BM)
- Part of the ECM.
- A 50-200 nm layer that underlies epithelial tissue.
- Also surrounds blood vessels, nerve fibers, muscles, and fat cells. Separates adjacent tissues within an organ.
- Provides mechanical support.
- Generates signals to maintain cell survival.
- Serves as a substratum for cell migration.
- Acts as a barrier to macromolecules (keeps proteins in the blood).
Basement Membrane (BM) - Roles
- Anchors epithelial cells to underlying connective tissue, maintaining tissue structure.
- Acts as a filter controlling the exchange of substances between the epithelium and adjacent tissues.
- Separates epithelial tissue from connective tissue ensuring distinct tissue boundaries.
- Provides cues for epithelial cell differentiation and aids in tissue repair.
- Provides structural support for endothelial cells maintaining the integrity of blood vessels.
- Regulates the passage of molecules between the bloodstream and surrounding tissues.
- Aids in endothelial cell migration and proliferation, especially during angiogenesis and wound healing.
- Prevents the mixing of endothelial cells with underlying tissues, ensuring functional compartmentalization.
Basement Membrane (BM) in Disease
- Glomerular basement membrane (GBM) filters blood while retaining cells and large proteins.
- Diabetes: GBM becomes very thick.
- Basement membrane disease: GBM becomes thin.
- GoodPasture's syndrome: GBM is disrupted and becomes thin.
- Thin Basement Membrane Disease: Genetically inherited condition affecting collagen.
- GoodPasture's syndrome: Autoimmune disease with antibodies against collagen.
Collagen
- The main structural protein in the ECM.
- The most abundant protein in the human body (more than 25%).
- Provides high tensile strength (1 mm diameter fiber can suspend ~22 lbs).
- Produced by fibroblasts, smooth muscle cells, epithelial cells, and other cells.
- 28 types of collagen fibers, each restricted to particular locations.
- A trimer formed by three polypeptide chains (α chains) wound around each other in a helix.
Collagen Structure
- α chains of collagen contain many hydroxylated proline residues.
- Hydroxylated proline residues maintain the stability of the triple helix.
- Hydroxyl groups are added to lysine and proline amino acids by Vitamin C (Ascorbic acid).
- Vitamin C deficiency can lead to scurvy, poor wound healing, hair changes, and skin bleeding.
Collagen Types
- Fibrillar collagens: Assemble into rigid, cable-like fibrils creating thicker fibers as a helical lattice (i.e., type I, II, III) - Provide mechanical framework for skin, tendons, vasculature, cornea, bone, and organs.
- Non-Fibrillar collagens: Non-helical lattice arrangement of collagens with globular domains (i.e., type IV) - Found in basement membranes and provide mechanical support with flexibility.
Collagen Genetic Mutations
- Type I Collagen Mutations: Osteogenesis Imperfecta ("brittle bone disease").
- Type II Collagen Mutations: Dwarfism.
- Type III Collagen Mutations: Ehlers-Danlos syndrome type IV.
- Type IV Collagen Mutations: Alport syndrome.
Tissue Organization - Endothelium
- Blood vessels composed of three primary layers: tunica intima, tunica media, and tunica adventitia.
- Tunica intima: Contains the endothelium, a single layer of endothelial cells lining the inner surface of the blood vessel.
- Tunica media: Middle layer composed of smooth muscle cells and elastic fibers.
- Tunica adventitia: Outer layer composed of connective tissue.
Cell-Cell/Cell-ECM Interactions
- Endothelial and epithelial cells are involved in cell-cell interactions and cell-extracellular matrix (ECM) interactions.
Intercellular Junctions
- Tight junctions: Seal the gap between cells.
- Adherens junctions: Connect actin filaments between cells.
- Desmosomes: Connect intermediate filaments between cells.
- Gap junctions: Allow the passage of small water-soluble molecules.
- Hemidesmosomes: Anchor intermediate filaments to the extracellular matrix (ECM).
- Focal adhesions: Anchor many cell types to the ECM.
Extracellular Components
- Glyocalyx
- Extracellular matrix (ECM):
- Basement membrane (BM)
Proteoglycans
- ECM protein-polysaccharide complexes composed of a core protein and glycosaminoglycans (GAGs).
- GAGs are highly acidic due to sulfate and carboxyl groups (negatively charged).
- Bind cations and water, forming a porous, hydrated gel resistant to crushing.
- Give cartilage and other ECM strength and resistance to deformation.
- Form gigantic complexes by binding together and linking with hyaluronic acid (a nonsulfated GAG).
Proteoglycans - Supplements
- Sulfated and nonsulfated GAGs are taken as health supplements to maintain skin and joint health.
Extracellular Matrix (ECM) Remodeling
- Dynamic structure with continuous degradation and reconstruction.
- Important for embryonic development, wound healing, and cancer metastasis.
Matrix Metalloproteinases (MMPs)
- Zinc-containing enzymes that degrade the ECM.
- Secreted into the ECM or anchored to plasma membranes.
- Digest nearly all ECM components.
- Involved in tissue remodeling, cell migration/invasion, wound healing, and neovascularization.
Cell-ECM Interactions: Integrins
- Membrane spanning polypeptide chains (α and β) - Non-covalently linked.
- 18 different α subunits and 8 different β subunits (~ 24 identified pairings).
- Integrate the extracellular and intracellular environments.
- Bind fibronectin, laminin, proteoglycans, and collagen - For example, they can bind Arg-Gly-Asp (RGD) sequences found in Fibronectin.
- Active integrins (“upright”) are triggered by internal cell signals, influencing the external environment ("inside-out signaling").
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Description
This quiz explores key components of cell biology, focusing on structures such as the endothelium, glycocalyx, extracellular matrix, and basement membrane. Each section highlights their functions and significance in tissue organization and cellular interactions.
