Cell Biology: Intermediate Filaments and Junctions

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Questions and Answers

What is the main function of communicating junctions?

To prevent the movement of proteins between cells

To provide structural support to cells

To facilitate nutrient absorption

To permit movement of ions or signaling molecules between cells (correct)

What type of proteins form a seal in tight junctions?

Claudins and occludins (correct)

Selectins and desmogleins

Cadherins and integrins

Catenins and adherens

Which junction type has a Ca2+-dependent mechanism?

Tight junctions

Zonula adherentes (correct)

Desmosomes

Gap junctions

Which is a characteristic feature of desmosomes?

Create small punctate attachments Signup and view all the answers

What structure is formed by the connection of two connexons?

A gap junction channel Signup and view all the answers

What is the composition of the plaques in desmosomes?

A series of attachment proteins Signup and view all the answers

What dimensions are gap junctions' intercellular channels typically characterized by?

About 1.5 nm Signup and view all the answers

Which type of junction provides a mechanical connection between cells through intermediate filaments?

Desmosomes Signup and view all the answers

What are the main structural components of intermediate filaments?

They consist of tetramers of rod-like proteins. Signup and view all the answers

Which type of intermediate filament is primarily found in epithelial cells?

Keratins Signup and view all the answers

What is the role of occluding junctions in cell biology?

To join cells and form an impermeable barrier. Signup and view all the answers

What type of junctions are macula adherens?

Spot-like junctions providing mechanical stability. Signup and view all the answers

Which statement is true regarding the individual subunits of intermediate filaments?

The subunits vary considerably between different types. Signup and view all the answers

Which type of junction functions to maintain cell-to-cell or cell-to-basal lamina adherence?

Anchoring junctions Signup and view all the answers

Which intermediate filament is associated with glial cells?

Glial fibrillary acidic proteins Signup and view all the answers

What type of structure do fascia junctions create between cells?

Broad areas of contact. Signup and view all the answers

Study Notes

Intermediate Filaments

Constructed from tetramers of rod-like proteins
Tightly bundled into helical arrays
Individual subunits vary based on filament type
Types include keratins, desmin, vimentin, glial fibrillary acidic protein, neurofilaments, and nuclear lamins

Intercellular Junctions

Specialized areas where cells connect
Classified morphologically into three types:
- Zonula (belt-like) junctions: Encircle cells completely
- Fascia (sheet-like) junctions: Form broad contact areas
- Macula (disc-like) junctions: Like spot welds on cell surfaces
Functionally classified into types:
- Occluding junctions: Form impermeable barriers
- Anchoring junctions: Provide mechanical stability
- Communicating junctions: Allow ion/molecule transfer

Cellular Junctions

Tight junctions (Zonula occludens):
- Encircle cells
- Formed by fusion of outer membrane layers
- Seal prevents paracellular transport
- Utilize claudins, occludins, and cadherins
Adherens junctions (Zonula adherens):
- Located below tight junctions
- Bind cells through cadherins
- Link to actin filaments
Desmosomes (Macula adherens):
- Spot welds connecting cells
- Have plaques that bind intermediate filaments
- Important for tissues under stress
Gap junctions (Nexus):
- Specialized channels between cells
- Made of connexons for ion/small molecule exchange

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Description

Explore the fascinating world of cell biology, focusing on intermediate filaments and intercellular junctions. Learn about the structure, types, and functions of these essential cell components, including their roles in maintaining cellular integrity and communication.