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CAPS 390 > L7. Cell Junctions > Flashcards

L7. Cell Junctions Flashcards

1
Q

What are the 4 different tissue types in the body?

A
  1. epithelium
  2. connective
  3. muscle
  4. nervous
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2
Q

What are cell junctions

A

allow the formation of tissues by connecting cells with other cells

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3
Q

Where are cell junctions most prominent?

A

epithelium cells

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4
Q

What locations can cell junctions be in a cell?

A
  • cell-cell interaction

- cell-ECM interaction

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5
Q

What types of cell junctions are there ( 3 types)

A
  • occluding ( sealing)
  • anchoring
  • channel-forming
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6
Q

Purpose of the occluding junctions

A

seal the contacts between cells

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7
Q

Purpose of the anchoring junctions

A

mechanically attach cells together

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8
Q

Purpose of the channel forming junctions

A

allows chemical and electrical junctions to pass through the cells

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9
Q

What are the 3 main types of proteins in adhesion complexes? State their characteristics

A
  1. Adaptor protein : allow recruitment of additional components to adhesion proteins, regulate adhesion complex
  2. Transmembrane adhesion protein: spans the cell membrane
  3. cytoskeletal linkers: physical link between adhesion complex and cytoskeletal linkers
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10
Q

Draw the full adhesion complex protein

A

L7 pg 4b.

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11
Q

Name the 4 cell-cell junctions

A
  1. zonular adherins ( anchoring )
  2. tight junctions ( sealing)
  3. desomosomes ( anchoring)
  4. gap junctions ( communicating)
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12
Q

Name the 2 cell-ECM junctions

A
  1. focal contacts ( anchoring)

2. hemidesosomes ( anchoring)

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13
Q

What are polarized cells

A

cells that have specialized domains

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14
Q

What are the 3 sides of the of the epithelial cell

A
  1. basal
  2. lateral
  3. apical
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15
Q

Draw where the 4 cell-cell junctions are in a polarized cell

A

L7 pg 6a

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16
Q

What composes the junctional complex?

A

the occluding junctions and anchoring junctions ( ie. desmosomes, tight junctions and zonular adherins)

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17
Q

What are the 3 ways that anchoring junction proteins resist the large force of the cell?

A
  1. multi-protein complex: redundancy
  2. cluster of adhesion proteins: combined strength
  3. link to cytoskeleton (adhesion protein) : large tension bearing protein interaction
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18
Q

What is freeze fracture used for?

A

look at junctional proteins

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19
Q

State the process of freeze fracture

A
  1. cells are frozen
  2. frozen cells are fractured, fracture is irregular
  3. thin layer is sprayed on surface to produce cast
  4. organic material is digested by acid- leaving replica
  5. replica is examined
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20
Q

What is the E-face

A

inner face of the outer lipid monolayer

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21
Q

What is the P-face

A

inner face of the inner lipid monolayer

22
Q

What is another name for tight junctions?

A

zonular occludens

23
Q

How are tight junctions formed

A

tight junctions formed through transmembrane protein interaction

24
Q

What are the 2 proteins that make up the tight junctions?

A

claudin and occludin

25
Q

Describe claudin

A
  • needed for tight junction formation

- 4-pass transmembrane protein

26
Q

Describe occlaudin

A

4-pass transmembrane protein receptor
barrier function
not needed for maintaining tight junction structure

27
Q

What is the function of tight junction

A

controls solute diffusion between body compartment (eg. glucose transport into blood-glucose blocked by diffusing between the cells -tight junctions, want to actively transport glucose through plasma membrane transporters )

28
Q

What happens when claudin 16 is lost

A

problem with tight junction
calcification in kidney
disrupt electrolyte cleaning

29
Q

another name for zonular adherens

A

adheren junctions

30
Q

What do adheren junctions form?

A

continuous adhesion belts

2D sheets of cells

31
Q

What makes adheren junctions/ zonular adherens?

A

cadherins (adhesion protein)

transmembrane protein

32
Q

What do adheren junctions link to

A

actin filaments

33
Q

how many pass is an adheren junction

A

single pass

34
Q

What is the structure of adherin junctions ( draw structure)

A

the cadherin cluster together (L7. pg 14a)

35
Q

How do adherin junction form?

A

cadherin molecules bind to other cadherins (aggregate)
cadherin extracellular domain straiten with calcium binding
cadherin cis-homodimer straightening allows trans homodimerization

36
Q

what is a trans homodimer

A

when (cadherin) molecule binds another molecule on the surface of ANOTHER cell

37
Q

what is a cis homodimer

A

when (cadherin) molecule binds another molecule on the surface of the same cell

38
Q

What are catenins?

A

They are adaptor proteins(INTRACELLULAR anchoring complex) that link the cadherin homodimers to the actin cytoskeleton

39
Q

draw relation between catenin, actin filaments and cadherins

A

(L7, pg 15b)

40
Q

What happens when cadherins are lost

A

tumor

41
Q

What is the alternative name of desmosomes

A

macula adherens

42
Q

What is the adhesion bases for desmosomes

A

-desmocolin and desmoglein ( cadherin like receptors)

43
Q

Which cytoskeletal element do desmosomes bind to

A

intermediate filaments (keratin family)

44
Q

What are desmosomes used for

A

strengthening tissue

45
Q

Where are desmosomes found

A

tissues exposed to tensile forces

46
Q

Draw the relation between cytoskeleton, intermediate filaments, dsc dsg ,linkers

A

pg 17 a

47
Q

What is pemphigus vulgaris

A

loss of dsg : skin blistering

48
Q

What are gap junctions for

A

allows cells to communicate and share nutrients

49
Q

Aside from epithelial cells where else are gap junctions formed

A

cardiomyocyte

smooth muscle

50
Q

What makes up gap junctions

A

connexin: gap junction protein
connexon: cluster of 6 connexins

51
Q

What is Vohwinkel Syndrome (keratodema)

A

Skin is hard and thick

loss of connexin 26

CAPS 390 (35 decks)

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