Biology: Cell Structure and Function

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Questions and Answers

What type of proteins bind via anchor proteins to intermediate filaments?

Desmoplakin

Plakoglobin

Plakophilin

Desmocollin and Desmoglein (correct)

What is the primary function of desmosomes?

To maintain tissue fluid balance

To provide mechanical strength to tissues (correct)

To regulate cell growth and division

To facilitate cell-cell communication

Which of the following proteins is NOT part of the cytoplasmic plaque?

Desmocollin (correct)

Plakoglobin

Plakophilin

Desmoplakin

What is the result of antibodies binding to desmosomal cadherins in autoimmune diseases such as pemphigus?

Disruption of desmosomes leading to skin blistering Signup and view all the answers

What is the structure that provides attachment sites for intermediate filaments in desmosomes?

Cytoplasmic plaque Signup and view all the answers

Which of the following tissues is NOT typically abundant in desmosomes?

Brain tissue Signup and view all the answers

What is the function of Desmoglein and Desmocollin in desmosomes?

To link adjacent cells together Signup and view all the answers

What is the name of the autoimmune disease that affects skin epithelial cells due to antibodies against desmosomal cadherins?

Pemphigus Signup and view all the answers

What is the result of a severe Desmoglein 3 defect?

Leakage of body fluids into the loosened epithelium Signup and view all the answers

What type of intermediate filaments are found in epithelial cells?

Keratin filaments Signup and view all the answers

What is the function of anchoring junctions?

Cell-cell and cell-matrix adhesion Signup and view all the answers

What is the characteristic of hemidesmosomes?

They have a single dense plaque on the cytoplasmic surface Signup and view all the answers

What is the function of integrins in hemidesmosomes?

Binding to laminin protein in the basal lamina Signup and view all the answers

What is the effect of autoantibodies attacking type XVII collagen?

Blisters in the skin Signup and view all the answers

What is the result of mutations in plectin?

Skin blisters and muscular dystrophy Signup and view all the answers

What is the function of hemidesmosomes in cell-matrix adhesion?

To anchor loops of intermediate filaments Signup and view all the answers

What type of junction is characterized by actin filament attachment sites?

Adherens junctions Signup and view all the answers

What type of collagen is targeted by autoantibodies in bullous pemphigoid?

Type XVII collagen Signup and view all the answers

What is the role of integrins in focal adhesions?

To bind to components of the extracellular matrix Signup and view all the answers

What is the consequence of mutations in plectin?

Skin blisters Signup and view all the answers

What type of filaments are attached to focal adhesions?

Actin filaments Signup and view all the answers

What is the function of anchoring junctions?

To anchor cells to the extracellular matrix Signup and view all the answers

What is the function of the cytoplasmic domain of the integrin in focal adhesions?

To bind indirectly to actin filaments Signup and view all the answers

What type of junctions are characterized by the presence of a dense plaque on the cytoplasmic surface?

Hemidesmosomes Signup and view all the answers

Study Notes

Anchoring Junctions

Anchoring junctions can be subclassified according to the cytoskeletal element involved
Two types of anchoring junctions:
- Actin filament attachment sites
  - Cell-cell junctions (ADHERENS JUNCTIONS)
  - Cell-matrix junctions (FOCAL ADHESIONS)
- Intermediate filament attachment sites
  - Cell-cell junctions (DESMOSOMES)
  - Cell-matrix junctions (HEMIDESMOSOMES)

Desmosomes

Desmosomes are strongest points of cell adhesion that provide mechanical binding
Most abundant in tissues that are exposed to mechanical stress (Epidermis of the skin, heart muscle)
Cell to cell binding depends on cadherin family of proteins called desmoglein and desmocollin
Desmosomes contain plaque-shaped structures on the cytoplasmic face of the junction which provide attachment sites for intermediate filaments
Plaque proteins: plakoglobins, desmoplakins, plakophilins

Hemidesmosomes

Hemidesmosomes resemble desmosomes morphologically
Hemidesmosomes have only a single dense plaque on the cytoplasmic surface of the hemidesmosome (hemi=half) that anchors loops of intermediate filaments
Hemidesmosomes connect epithelial cells to the basal lamina
Integrin (α6β4) and type XVII collagen (also called BPAG2) attach to the basal lamina

Importance of Desmosomes and Hemidesmosomes

In a blistering skin disease called bullous pemphigoid, autoantibodies attack type XVII collagen
Mutations in plectin cause skin blisters associated with late-onset muscular dystrophy
Cataract, heart malformations, and skin blistering are examples of diseases related to desmosome and hemidesmosome dysfunction

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Description

This quiz covers the structure and function of cells, including desmoglein, pemphigus vulgaris, and types of intermediate filaments in different cell types.