cell junctions

Question 1

different types of cell junctions

Answer 1

-tight junctions
-cell-cell anchoring junctions
-channel forming junctions
-cell matrix anchoring junctions

Question 2

what are Adherens Junctions

Answer 2

-Cadherins e.g. E(pithelial)-cadherin- allows interaction with other cells
-cadherins are Ca2+ Dependent
-Homophilic interaction- binding to cadherins on other cells
-Makes strong links between cells
-Links to actin cytoskeleton
-belta desmosomes- junctions connected to actin cytoskeleton forming a belt

Question 3

what are the 2 types of actin-linked junctions

Answer 3

-adherens junctions
-focal adhesion

Question 4

whats The Adhesion Belt in Morphogenesis

Answer 4

-cadherin-> catenin-> actin-> myosin
1) sheet of epithelial cells with adhesion belt associated with actin filament
2) invagination of epithelial sheet caused by an organised tightening along adhesion belts in selected regions of cell sheet (top of cytoskeleton contracts and curls)
3) epithelial tube pinches off from overlying sheet of cells
4)-> epithelia tube formed
-have E and N-cadherins - different stains for the different ones

Question 5

whats are Desmosomes And Hemidesmosomes

Answer 5

-Focal Adhesions and Adherens Junctions link to the actin cytoskeleton
-Hemidesmosomes:
=Attach Cells To Basal Lamina
=Integrins And Intermediate Filaments
-Desmosomes:
=Cell - Cell Junctions
=Cadherins And Intermediate Filaments
=Plentiful in heart muscle and epidermis

Question 6

integrin vs cadherin

Answer 6

-integrin: actin= focal adhesion, intermediate filament = hemidesmosomes
-cadherins: actin= adherens junctioons, intermediate filament= desmosome

Question 7

what do desmosomes contain

Answer 7

-keratin filaments- anchored to cytoplasmic plaque
-intermediate filaments
-cadherin family proteins
-cytolasmic plaque made of intracellular anchor proteins

Question 8

whats Pemphigus

Answer 8

-Desmoglein
-Hold together keratinocytes in epidermis
-Autoimmune Skin Blistering
-issues in the desmoglin

Question 9

whats the Role of Tight Junctions

Answer 9

-Locations
=Epithelia e.g. Gut
-roles:
=To Prevent Fluid, Ion and Membrane Flow
=Variable Extent
=Transcellular Transport
=Paracellular Transport

Question 10

whats the Tight Junction Structure

Answer 10

-focal connection
-plasma membrane
-ridges in transmembrane particles forming sealing strands

Question 11

Tight Junction Proteins

Answer 11

-sealing of strands of occluding and Claudin proteins
-Zonula occludens proteins bind claudin, occludin and actin
-one type of occludin
-25 claudins

Question 12

what are Defining Membrane Compartment

Answer 12

-Specialisation Of Membrane Regions
-Lipids And Proteins Segregated
-Apical Outer Membrane:
=Glycolipid
=Cholesterol
-Basolateral:
=Phosphatidylcholine

Question 12

what are Gap Junctions

Answer 12

-100 - 500 nm long
-Close apposition of membranes:
=gap = 2- 4 nm
-Wide distribution
-Connective tissue, epithelia, neurons, heart muscle
-Allows regulated and direct cell-cell communication
-Form 1.5 nm diameter pores
-Water, inorganic ions, sugars, amino acids, ATP, cAMP, IP3

Question 13

whats the Gap Junction Structure

Answer 13

-Gap junctions made of connexins
-large number of different types of channels can be formed for regulation and different permeabilities because of the large number of variations you can use
-can have either homomeric ir heteromeric (the same or different connexions)
-tercellular channels= homotypic or heterotypic (heterotypic can be half and half or mixed up)
-gap of 2-4nm
-channel diameter is 1.5nm

Question 14

how are gap junctions used for regulation

Answer 14

-Membrane potential, pH, Ca2+ and cell signals
-gap junctions slam close, neurones still is damaged, but everything around it is fine because the junction is regulated
-Limit damage caused by calcium influx