Cell-Cell junctions Flashcards
What are tight junctions also known as?
Occluding junctions
What do tight/occluding junctions do?
Act as a barrier layer between cells
What do cell-cell / adherens junctions do?
→ hold layer together
→ leaves space between
What do channel/gap junctions do?
→ allow cells to work together
What do cell-matrix focal adhesion junctions do?
→ connect cells to the matrix using integrins
Describe adherens junction
cell-cell
- Ca2+ dependent
- Transmembrane receptor (cadherin) forms homophilic interaction with adjacent cell
= Make strong links between cells (tensile strength)
What does controlling the distribution of cadherin expression do?
controlling where invaginations form
E.g image shows formation of neural tube in embryo
Describe hemidesmosomes
- Attach Cells to the Basal Lamina (Focal Adhesion)
- Contain integrins that link to the intermediate filaments
Describe desmosomes
- Cell-cell junctions (Adherens Junctions)
- Contain cadherins that link to intermediate filaments (keratin)
Describe the role of tight/ occluding junctions
To prevent fluid, ion and membrane flow → can be controlled variably
What are the 2 types of transport found in tight junctions.
Transcellular
Paracellular
Describe transcellular transport
Involves endocytosis on apical/basal face then excretion on basal/apical face
Requires energy
Describe paracellular transport
Passive transport through barrier layer between cells (leaky junctions)
Selective, variable and regulated
No energy required, but materials only move down conc. gradient
Name some proteins present in tight junctions
Occludin (only 1 type)
Claudin (~25 types = different permeabilities)
Zonula occludens proteins bind claudin, occulin & actin
Name 2 molecules typically found in the apical membrane
Glycolipid
Cholesterol
