Junctions

Question 1

Tight junction

Answer 1

First barrier that protects the cells

transmembrane proteins at top that hold onto each other and stop things from leaking down

membrane proteins: occludins, claudins
cytosolic proteins: actin, ZO-1

occludins grab on actin inside the cell

Question 2

zonula adheren

Answer 2

inside cell: alpha-actinin, vinculin (actin binding protein)

transmembrane protein: Cadherins

intercellular space: 15 nm (bigger due to transmembrane proteins – cadherins. Form heterodimers or homodimers)

Question 3

gap junction

Answer 3

channel between membranes allow for ion passage. Line up together on cell membrane 2 nm

Coupled connexons connect PMs (connexons composed of 6 connexins) How cells communicate with each other

not a real junction complex

Question 4

desmosome

Answer 4

macula adherens
strongest junction due to tonofilaments (intermediate filaments)

electron-dense material: plaque (made of proteins).

inside plaque: desmoplakins I&II, plakoglobin, desmocalmin

intercellular space 25 nm- bigger due to transmembrane proteins: desmocollin and desmoglein (belongs to cadherins) Make hetero/homodimers

Question 5

hemidesmosome

Answer 5

plaque contains BP 200 protein

intermediate filaments (tonofilaments)

transmebrane proteins attaches type 7 collagen: alpha 6 integrin, beta 4 integrin, BP180

the term BP us related to Bullous Phemphigoid (disease where plaques stop working)