L5 - cell adhesion and junctions Flashcards

1
Q

define cell junction

A

the structures that enable cell adhesion (junctional complexes)

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2
Q

how many types of cell junctions are there

A

6

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3
Q

name the types of cell junctions (junctional complexes)

A
  1. desmosomes/hemidesmosomes (2)
  2. tight junctions
  3. gap junctions
  4. adherens junction
  5. focal adhesions
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4
Q

name the two types of extracellular matrices

A
  1. basement membrane (basal lamina)

2. fibrillar matrix

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5
Q

what is the basal lamina

A

type of ECM

a 2D sheet that epithelial cells sit on

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6
Q

what is the fibrillar matrix

A

type of ECM
3D matrix composed of various fibres, in
which cells such as fibroblasts are buried

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7
Q

what are main components of basal lamina

A

collagen IV
laminin
nidogen
perlecan

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8
Q

what type of cell junction are desmosomes

A

cell - cell anchoring junctions

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9
Q

main components of the fibrillar matrix

A

Collagen I
Fibronectin
Elastin
Proteoglycans

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10
Q

describe appearance of desmosomes

A

pairs of dark disk like structures at cell - cell contacts

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11
Q

function of desmosomes

A

connect cell - cell
anchor the intermediate filaments of adjacent cells (indirectly) to eachother
provide mechanical strength

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12
Q

describe appearance of hemidesmosomes

A

appear like half desmosomes

half disk like structures at the cell - ECM junction

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13
Q

what type of cell junction are hemidesmosomes

A

cell - matrix anchoring junctions

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14
Q

function of hemidesmosomes

A

connect cell - ECM
anchor the intermediate filaments of cells to the ECM
mechanical strength

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15
Q

what type of cell junction are tight junctions

A

occluding junctions

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16
Q

what type of cell junctions are gap junctions

A

channel - forming junctions

17
Q

what type of cell junction are focal adhesions

A

cell - matrix anchoring junctions

18
Q

what type of cell junction are adherens junctions

A

cell-cell anchoring junctions

19
Q

describe appearance of tight junctions

A

a point where two membranes of cells come together with no gap
located closer to apical side
surround entire cell like a headband

20
Q

function of tight junctions

A
  1. act as ‘fence’ apical and basolateral TRANSMEMBRANE proteins cant diffuse between tight junctions, so the apical ones are kept on the apical side and the basolateral ones on the basolateral side so they can carry out their correct functions
  2. also act as a permeability barrier for molecules in EC fluid
21
Q

describe appearance of gap junctions

A

a point where two membranes of cells come together with a gap - lateral surface

22
Q

function of gap junctions

A

canal between cells allowing movement of ions and small molecules when open

23
Q

where is adherens junction located

A

beneath tight junctions like another headband

24
Q

main component of adherens junction

A

cadherin

25
Q

function of adherens junction

A

maintain cell - cell adhesion - cell reassembly

involved in contraction (during epithelial folding)

26
Q

function of cadherins found in adherens junction

A

homotypic adhesion that causes cell sorting

27
Q

how is the adherens junction involved in contraction (leading to epithelial folding)

A

Cadherins in AJ are linked to the circumferential actomyosin bundle that contracts during epithelial folding
this squeezes the ‘headband’ of cell
results in folding - to form tubes etc

28
Q

what are focal adhesions

A

large multimolecular assemblies that contain integrins and attach cell to ECM

29
Q

how do focal adhesions attach to ECM

A

integrins of focal adhesions bind to ECM outside the cell and connect to actin filaments inside the cell

30
Q

where are focal adhesions located

A

basal membrane

31
Q

function of focal adhesions

A

involved in exerting force and movement of cells

32
Q

differences between hemidesmosomes and focal adhesions

A

hemidesmosomes connect too IF , FA connect to AF
HD resist force , FA exert force
HD anchor to matrix , FA move on matrix

33
Q

where is the fibrillar matrix located

A

under basal lamina