BCT Cell Junctions and Surface Modifications

These flashcards cover key concepts related to cell junctions and surface modifications, including definitions, functions, and structural characteristics.

What are cell junctions?

Cell junctions are specialized attachments between adjacent cells that modify the plasma membrane to provide anchoring of adjacent cells and cytoplasmic continuity.

What is the function of tight junctions (Zonula Occludens)?

Tight junctions seal cell-lined compartments, preventing the passage of water-soluble molecules between cells.

How do adherens junctions function?

Adherens junctions involve calcium-dependent cadherins that bind adjacent cells together and anchor actin microfilaments to strengthen the tissue.

What is the difference between desmosomes and adherens junctions?

Desmosomes are similar to adherens junctions but are disc-shaped and use cytoplasmic intermediate filaments to anchor cadherins.

What do hemidesmosomes do?

Hemidesmosomes attach cells to components of the extracellular matrix using integrins and anchor the cytoskeleton to the basal lamina.

What is the role of gap junctions (Nexus)?

Gap junctions allow for the passage of ions and small molecules between adjacent cells, functioning as communicating junctions.

What is a terminal bar?

The terminal bar is a group of junctional complexes that attach adjacent epithelial cells, including tight junctions, zonula adherens, and desmosomes.

Describe the structure of microvilli.

Microvilli are about 1μm long, covered with glycocalyx, have a core of actin filaments arranged longitudinally, and are not motile.

How do cilia differ from microvilli?

Cilia are motile structures that have an axoneme (9+2 arrangement of microtubules), while microvilli are non-motile and increase surface area.

What is glycocalyx?

Glycocalyx is a coating of glycoproteins and glycolipids on the plasma membrane that is important for cell-to-cell recognition.