adhesion molecules

Question 1

4 types of cell-cell junctions in epithelia

Answer 1

adherens junctions
desmosomes
tight junctions
gap junctions

Question 2

3 functional categories of cell cell junctions

Answer 2

anchoring junctions
tight junctions
gap junctions

Question 3

protein that mediates adherens junctions

Answer 3

classical cadherins

Question 4

what are adherens junctions connected to

Answer 4

actin cytoskeleton

Question 5

what are the classical cadherins

Answer 5

ENP cadherins

Question 6

what do cadherins do

Answer 6

calcium binds to cadherins and stabilises the flexible linkers
this facilitates binding of cadherins between cells

Question 7

experimental evidence of cadherins in cell adhesion

Answer 7

E cadherin introduced to L cells and E cadherin was found to preferentially adhere to other E cadherin cells via calcium dependent aggregation

Question 8

adaptor protein in adherens junctions

Answer 8

alpha and beta catenin

Question 9

how do desmosomes differ from adherens junctions

Answer 9

they use desmosomal cadherins (desmoglein, desmocollins) rather than classical ones

Question 10

what are desmosomes connected to

Answer 10

intermediate filaments

Question 11

what adaptor proteins are associated with desmosomes

Answer 11

desmoplakin

Question 12

another name for tight junctions

Answer 12

zona occludens

Question 13

function of tight junctions

Answer 13

form a seal between cells preventing movement of water and solutes between cells
prevents movement of membrane lipids between apical and basolateral surface

Question 14

protein components of tight junctions

Answer 14

occludins and claudins

Question 15

adaptor protein in tight junctions

Answer 15

ZO-1

Question 16

structure of occuludins and claudins

Answer 16

have transmembrane domains forming loops that form non covalent interactions with loops from adjacent cell

Question 17

what are gap junctions made of

Answer 17

connexin proteins, one from each cell and they join in the middle

Question 18

structure of connexon

Answer 18

6 connexion proteins in a wheel shape

Question 19

why are gap junctions diverse

Answer 19

they can be homomeric or heteromeric depending of the connexin used
also homotypic/ heterotypic

Question 20

function of gap junctions

Answer 20

allow small molecule transport
intergrate metabolic processes by passing secondary messengers to adjacent cells
facilitate rapid transmission of electric signals in neurons

Question 21

structure of plasmodesmata

Answer 21

gap junction in plants, plasma membranes merge to for annulus channel, extension of ER called desmotubule