Cell Biology: Extracellular Interactions

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Questions and Answers

What is the primary role of epithelium in the body?

Nutrient absorption

Cell movement

Fluid secretion

Covering surfaces and lining cavities (correct)

What is one function of endothelium within blood vessels?

Regulation of blood pressure (correct)

Production of hormones

Protection against pathogens

Energy storage

Which layer of the skin is composed of dense, irregular connective tissue?

Subcutaneous layer

Epidermis

Basement membrane

Dermis (correct)

Which process is NOT primarily regulated by interactions between cells and their environment?

Cell death Signup and view all the answers

What critical function does skin serve beyond being a covering?

Sensory perception Signup and view all the answers

How do cells primarily maintain their defined relationships in tissues?

By interacting with extracellular materials Signup and view all the answers

Capillaries are lined with what type of cells?

Epithelial cells Signup and view all the answers

What element is critical for the 3-D organization of tissues and organs during embryo development?

Cell migration Signup and view all the answers

What is the primary role of the glomerular basement membrane (GBM) in the kidneys?

Filters blood while retaining cells and large proteins. Signup and view all the answers

Which condition is characterized by a thickened glomerular basement membrane (GBM)?

Diabetes Signup and view all the answers

What type of collagen is most abundant in the human body?

Collagen type I Signup and view all the answers

What is a possible effect of Vitamin C deficiency related to collagen?

Scurvy leading to poor wound healing. Signup and view all the answers

Which type of collagen is primarily found in the cartilage?

Collagen type II Signup and view all the answers

What genetic condition is associated with collagen type I abnormalities?

Osteogenesis Imperfecta Signup and view all the answers

What role does hydroxylated proline play in collagen structure?

Stabilizes the triple helix of collagen. Signup and view all the answers

Which type of collagen provides mechanical support with flexibility and is found in basement membranes?

Collagen type IV Signup and view all the answers

Which condition presents with distinct facial appearance, bruising, and skin thinning due to type III collagen issues?

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

What is the main source of collagen production in the body?

Fibroblasts 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 type of junction connects actin filaments between cells?

Adherens junctions Signup and view all the answers

What role does the glycocalyx play in cellular interactions?

Mediates cell-cell and cell-substratum interactions Signup and view all the answers

Which structure anchors intermediate filaments to the extracellular matrix?

Hemidesmosomes Signup and view all the answers

What is the primary component of the extracellular matrix that strengthens tissue?

Basement membrane Signup and view all the answers

What is one of the main functions of the endothelial cells?

Providing a protective lining for blood vessels Signup and view all the answers

Which disease is characterized by damage to the glycocalyx?

Atherosclerosis Signup and view all the answers

What is a primary role of the extracellular matrix (ECM)?

Providing physical and biochemical signals Signup and view all the answers

Which of the following best describes the basement membrane?

Part of the extracellular matrix that underlies epithelial tissue Signup and view all the answers

In which of the following ways does the basement membrane assist epithelial cells?

Anchoring epithelial cells to connective tissue Signup and view all the answers

What is the significance of the dynamic nature of the extracellular matrix?

It's continually degraded and reformed, affecting cellular activity. Signup and view all the answers

Which of the following is NOT a function of the basement membrane?

Storing metabolic waste products Signup and view all the answers

How does the extracellular matrix contribute to tissue repair?

It provides cues for epithelial cell differentiation. Signup and view all the answers

What is the primary function of fibronectin in the extracellular matrix?

Cell adhesion and migration Signup and view all the answers

Which sequence allows fibronectin to bind to integrins?

Arg-Gly-Asp Signup and view all the answers

What structural feature do laminins share?

Three polypeptide chains linked by disulfide bonds Signup and view all the answers

Which cells primarily secrete fibronectin?

Fibroblasts Signup and view all the answers

What is a primary role of laminin in embryonic development?

Guiding cell migration of primordial germ cells Signup and view all the answers

Which components does fibronectin NOT bind to?

Lipids Signup and view all the answers

How are fibronectin monomers structured?

Two nearly identical monomers linked by disulfide bonds Signup and view all the answers

Which of the following is a function of laminin?

Cell growth and differentiation Signup and view all the answers

Study Notes

Extracellular Interactions

Cells in multicellular organisms are organized into tissues
Cells interact with each other and extracellular materials
These interactions regulate cell migration, growth, differentiation, and 3D tissue organization

Tissues

Epithelium: A thin layer of tightly packed cells that cover surfaces and line cavities
- Examples: epidermis (outer layer of skin)
Endothelium: Specialized epithelium found inside blood vessels and lymphatic vessels
- Single cell layer, controls bloodflow, regulates blood pressure, facilitates nutrient and waste exchange

Cell-Cell/Cell-ECM Interactions

Apical Surface:
- Tight Junctions: Seal gap between cells
- Adherens junctions: Connect actin filaments between cells
- Desmosome: Connects intermediate filaments between cells
- Gap Junction: Passage of small water-soluble molecules
- Hemidesmosome: Anchors intermediate filaments to extracellular matrix
Basal Surface:
- Focal adhesions: Anchors many cell types to ECM

Extracellular Components

Glycocalyx: 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
Extracellular Matrix (ECM): Organized network of extracellular material
- Provides physical and biochemical signals
- Basement Membrane is part of the ECM, located beneath epithelial tissue and surrounds blood vessels, nerve fibers, muscles, and fat cells
- Separates adjacent tissues, provides mechanical support, generates signals for cell survival, serves as substratum for cell migration, and acts as a barrier to macromolecules

Basement Membrane in Disease

Glomerular basement membrane (GBM) filters blood in the kidney
- Abnormal GBM impairs kidney filtration
- Examples:
  - Diabetes: GBM thickens
  - Basement membrane disease: GBM becomes thin
  - GoodPasture’s syndrome: GBM is disrupted and thin

Basement Membrane Roles

For Epithelium:
- Anchorage: Anchors epithelial cells to connective tissue
- Filtration: Controls substance exchange between epithelium and adjacent tissues
- Compartmentalization: Separates epithelium from connective tissue
- Cell differentiation and regeneration: Guides epithelial cell differentiation and repair
For Endothelium:
- Structural support: Provides a foundation for endothelial cells
- Selective barrier: Regulates molecule passage between blood and tissues
- Cell migration and repair: Aids endothelial cell migration and proliferation during angiogenesis and wound healing
- Maintains separation: Prevents mixing of endothelial cells with underlying tissues

Extracellular Matrix Proteins

Collagen: Main structural protein in ECM, most abundant protein in the human body, has high tensile strength
- Types:
  - Fibrillar: Assemble into rigid, cable-like fibrils that package into thicker fibers. Found in skin, tendons, vasculature, cornea, bone, and organs
  - Non-Fibrillar: Non-helical lattice arrangement with globular domains found in basement membranes.
Fibronectin: Glycoprotein secreted by fibroblasts, initially soluble, cells use it to build insoluble matrix
- Plays a major role in cell adhesion, growth, migration, differentiation, wound healing, and embryonic development
Laminin: Family of extracellular glycoproteins, organized into a cross-shaped molecule
- Binds to cell-surface receptors, other laminin molecules, proteoglycans, and collagen of the basement membrane
- Important for cell migration, growth, and differentiation

Collagen - Structure

α chains of collagen: Contain hydroxylated proline residues
- Contribute to stability of the triple helix structure
- Vitamin C adds hydroxyl groups to lysine and proline, crucial for collagen structure
Vitamin C deficiency: Leads to scurvy (poor wound healing, hair changes, skin bleeding)

Collagen - Types and Genetic Mutations

Type I: Most abundant, found in tendons, skin, vessel walls, fibrocartilage, bones, and teeth
- Mutations: Osteogenesis Imperfecta (brittle bone disease)
Type II: Makes up 50% of cartilage protein
- Mutations: Dwarfism
Type III: Found in wound healing, vessel walls, skin, intestines, and the uterus
- Mutations: Ehlers-Danlos Syndrome (type 4)

Fibronectin - Structure

Binds to integrins (membrane-spanning receptor proteins) via Arg-Gly-Asp sequence
Also binds to ECM via collagen, fibrin, and proteoglycans
Protein dimer: Composed of 2 nearly identical monomers linked by disulfide bonds, containing distinct modules

Laminin - Functions

Plays a pivotal role in the migration of primordial germ cells (PGCs)
- PGCs arise in the yolk sac and travel to the developing gonad via regions rich in laminin.

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Description

Explore the fundamental interactions between cells and their surrounding extracellular matrix in multicellular organisms. This quiz covers the organization of tissues, various types of epithelium, and the specific cell-cell and cell-ECM junctions that facilitate critical biological processes. Test your knowledge on how these interactions impact cell behavior and tissue formation.