Question

Would you please be able to compare and contrast these following terms using structures and detailed explanation underneath. Also make sure to indicate the cytoskeletal attachment, it's  function and the location of each structure.

Tight junctions

Adherens junctions

Desmosomes

Hemidesmosomes

and Focal Adhesions.

Thanks!

Answer 1

Occluding Junctions :

Tight junction is a type of occluding junction which is a cell-cell junction mediated by two transmembrane proteins - claudin and occluding.

Function :Tight junctions prevent free passage of molecules (even ions).

Adherens junction :

It is a type of Anchoring junction which connects bundles of actin filaments from cell to cell or cell to extracellular matrix. Transmembrane protein is cadherin.

Function : Stabilises cell adhesion, regulates actin cytoskeleton, regulates transcription and intracellular signalling

Focal adhesion :

It connencts the cell to matrix through a transmembrane adhesion protein of integrin family and actin filament. Intracellular linkage is through actin filaments

Function : Connects cell cytoskeleton to ECM.

Desomosomes:

These are button like points of intercellular contacts which bind neigbouring cells together. On the cytoplasmic suface of each interacting plasma membrane a cytoplasmic plaque is present which is composed of intracellular attachment proteins. Each plaque is associated with a network of keratin filaments. Transmembrane linker proteins , which belong to cadherin family of cell - cell adhesion bind to plaques and interact to the extracellular domains to hold adjacent cells together. Intracellular linkage is through intermediate filaments.

Function : It gives mechanical strength to tissues.

Hemi- desmosomes :

They resemble desmosomes but join adjacent epithelial cell memberanes. They connect the basal surface of epithelial cells to underlying basal lamina. Transmembrane linker protein for hemi-desmosomes belong to the Integrin family rather than cadherin family used by desomosomes. Intracellular linkage is through intermediate filaments.

Function - Facilitate stable adhesion of epithelial cells to the basement membrane