Cell Biology: Extracellular Structures

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Questions and Answers

Which of the following roles is NOT associated with the extracellular matrix (ECM)?

Provides biochemical signals to cells

Maintains the shape of tissues

Serves as a barrier against external pathogens (correct)

Regulates cell migration and proliferation

What is the significance of the basement membrane in epithelial tissues?

Serves as a site of energy production

Exclusively provides mechanical support

Acts as a reservoir for nutrients

Guides cell differentiation and maintains tissue organization (correct)

How does the deletion of the extracellular matrix impact cellular activity?

Enhances cell adhesion and proliferation

Eliminates communication signals between cells (correct)

Reduces the need for cell differentiation

Increases the metabolic activity of cells

Which condition is associated with damage to the glycocalyx?

Atherosclerosis Signup and view all the answers

What is the primary component of the basement membrane?

Proteoglycans Signup and view all the answers

Which of the following statements about the roles of endothelial cells is incorrect?

They regulate gene expression in adjacent tissue. Signup and view all the answers

What role does the basement membrane play in relation to endothelial cells?

It provides a selective barrier for molecular exchange. Signup and view all the answers

In what way does the extracellular matrix contribute to tissue dynamics?

It actively degrades and reforms to adapt structurally. Signup and view all the answers

What role do proteoglycans primarily play in cell migration?

They greatly influence a cell's potential for migration, growth, and differentiation. Signup and view all the answers

Which of the following describes the structure of proteoglycans?

They are made up of a core protein and glycosaminoglycans covalently attached to it. Signup and view all the answers

What is a significant function of matrix metalloproteinases (MMPs)?

They degrade the ECM and are involved in tissue remodeling. Signup and view all the answers

How do integrins contribute to cellular interaction with the extracellular matrix?

They bind various proteins and integrate extracellular signals into the cell. Signup and view all the answers

What process is crucial for the remodeling of the extracellular matrix?

Continuous degradation and reconstruction of its components. Signup and view all the answers

What primary structural role does collagen play within the extracellular matrix?

Provides mechanical support and tensile strength Signup and view all the answers

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

Collagen type IV Signup and view all the answers

What is the primary consequence of a deficiency in vitamin C regarding collagen?

Impaired stabilization of the collagen triple helix Signup and view all the answers

Goodpasture’s syndrome is characterized by which of the following?

Thinning and disruption of the glomerular basement membrane Signup and view all the answers

Which characteristic is true regarding fibrillar collagens?

They assemble into rigid, cable-like fibrils Signup and view all the answers

Which genetic mutation is associated with collagen type I?

Osteogenesis Imperfecta Signup and view all the answers

The mechanical properties of skin and tendons primarily depend on which type of collagen?

Collagen type I Signup and view all the answers

Which condition is linked to collagen type III mutations?

Ehlers-Danlos Syndrome (type 4) Signup and view all the answers

How does thin basement membrane disease primarily affect kidney function?

Impairs the kidneys' ability to filter blood effectively Signup and view all the answers

What is a common outcome of vitamin C deficiency related to collagen health?

Decreased collagen cross-linking Signup and view all the answers

What is the primary function of tight junctions in cell-cell interactions?

Seal gaps between cells Signup and view all the answers

Which junction connects actin filaments between cells?

Adherens Junction Signup and view all the answers

What do hemidesmosomes primarily anchor to?

Extracellular matrix Signup and view all the answers

What component primarily mediates cell-cell and cell-substratum interactions?

Glycocalyx Signup and view all the answers

What type of junction allows the passage of small water-soluble molecules?

Gap Junction Signup and view all the answers

Which of the following types of junctions are characterized by connections of intermediate filaments?

Desmosomes Signup and view all the answers

Which structure is primarily found at the basal surface of epithelial cells?

Hemidesmosomes Signup and view all the answers

Which of the following best describes focal adhesions?

Specialized structures anchoring cells to the extracellular matrix Signup and view all the answers

What is the composition of the glycocalyx?

Glycoproteins and glycolipids Signup and view all the answers

What type of junction is least likely to be found in connective tissue?

Tight Junction Signup and view all the answers

What is the role of the tunica intima in blood vessels?

It facilitates nutrient and waste exchange. Signup and view all the answers

Which layer of blood vessels contains elastic fibers?

Tunica Media Signup and view all the answers

What is NOT a function of the endothelial layer of the tunica intima?

Providing structural support Signup and view all the answers

Which statement accurately describes the tunica adventitia?

It provides structural support and contains small blood vessels. Signup and view all the answers

Cell-cell and cell-ECM interactions are crucial for which of the following?

Cellular adhesion Signup and view all the answers

What primarily distinguishes the tunica media from the other layers of blood vessels?

Contains smooth muscle cells and elastic fibers. Signup and view all the answers

Which layer of the blood vessel is primarily involved in controlling blood flow?

Tunica Media Signup and view all the answers

The basal lamina is a component of which structure?

Extracellular Matrix (ECM) Signup and view all the answers

What keeps endothelial and epithelial cells together?

Cell-cell and cell-ECM interactions Signup and view all the answers

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.