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Cell Bio > Epithelium 2 > Flashcards

Epithelium 2 Flashcards

1
Q

Junctional complexes are found pretty much in every types of cells except…

A

blood cells

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2
Q

When referring to the apical portion of the cell domain, which part of the cell does it pertain to?

A

top

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3
Q

What are zonula occludens and where are they normally found in a cell?

A

tight junctions normally found near the apical portion of the lateral domain

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4
Q

Where are zonula adherens normally found in a cell?

A

immediately below zonula occludens

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5
Q

What are maculae adherens?

A

desosomes: spot connections between two cells (think of staples between two sheets of paper)

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6
Q

In what order will you find the junctional complexes in the epithelium?

A

zonula occludens (apical)
zonula adherens
macula adherens

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7
Q

What is another name for gap junction?

A

nexus

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8
Q

Where do you find hemidesmosomes?

A

in basal domain

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9
Q

What is the general blueprint for a junctional complex?

A

1) cytoskeletal elements (actin microfilaments or intermediate filaments)
2) intracellular anchor proteins
3) CAMs (aka transmembrane adhesion proteins)

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10
Q

What does intracellular anchor proteins anchor?

A

connects cytoskeletal component to CAMs

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11
Q

What are occludins and claudins and what do they do?

A

CAMs, they form tight connection with one another (ex. occludin from one cell connects to the occludin of the next cell, not occludin to claudin)

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12
Q

What does the baterium Helicobacter pylori do to zonula occludens?

A

disrupts occludins (tight junctions) in the stomach, making cells more susceptible to acidic injury

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13
Q

What does cholera toxins do to zonula occludens?

A

toxic to zonula occludens proteins (intracellular), dirsupts the junctional complex, leading to loss of fluids

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14
Q

Gene encoding for a specific claudin in renal epithelial cells results in what?

A

excessive loss of magnesium ions in urine

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15
Q

Which claudin protein is lost in brain cancers?

A

claudin 5

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16
Q

Which missing claudin protein can cause deafness?

A

claudin 9

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17
Q

Why is the ratio of claudins to occludins important?

A

ratio of claudins to occludins dictates the degree of permeability that exist in tight junctions.

18
Q

If you want less permeability in tight junctions, which should be higher? Claudins or occludins?

A

high claudins and low occludins

19
Q

What would the ratio of claudin to occludin be in the blood brain barrier?

A

high occludin and low claudin (low permeability)

20
Q

What role do tight junctions play in establishing polarity within a cell?

A

tight junctions keep receptors at the apical domain because they can’t cross, this allows for establishment of polarity within the cell

21
Q

What type of cytoskeletal elements will you find in macula adherens?

A

intermediate filaments (not actin)

22
Q

What’s an example of CAM found in zonula adherens?

A

E-cadherin

23
Q

What kind of CAMs can be found in macula adherens?

A

desmocollin and desmoglein

24
Q

What causes Pemphigus?

A

the body produces antibodies against demogleins (important CAM found in desmosomes)

25
Q

What are focal adhesions?

A

anchors cell to proteins of the ECM

26
Q

What kind of CAMs can be found in focal adhesions?

A

integrin

27
Q

What is hemidesmosome?

A

anchor basement domain of cell to underlying basal lamina

28
Q

What transmembrane protein is involved in hemidesmosomes?

A

collagen type XVII

29
Q

What is bullous pemphigoid?

A

body produces antibodies against collagen XVII, causes separation between the cell and basal lamina allowing fluid to build up in between

30
Q

Based on the general blueprint for junctional complexes, what component does integrin represent?

A

CAM

31
Q

What do nexus (gap junctions) do?

A

allow cells to communicate with each other

32
Q

What transmembrane protein (CAM) can be found in nexus?

A

connexins

33
Q

Describe the structure of connexon.

A

made up of 6 connexins

34
Q

Why would disruptions in nexus cause cardiac arrhythmias?

A

cardiac muscles have to contract in unison, without gap junctions, the cells cannot communicate with each other

35
Q

What other conditions can disruptions of nexus cause?

A
  • female infertility
  • neuropathy
  • deafness
  • congenital cataracts
36
Q

What can cause loosening of junctional complexes?

A

mutation in cadherin, catenin, or integrin

37
Q

Where are catenin and vinculin found?

A

intracellular proteins found in zonula adherens

38
Q

What does loosening of junctional complexes provide for cancer cells?

A

the ability to become motile (one of the steps to become metaplasia)

39
Q

What type of molecule is cadherin?

A

CAM

40
Q

Loss of cadherin is found in what and why?

A

cancerous cells because junctional complexes have been disrupted

41
Q

What does altered expression of integrin do?

A

allow cells to migrate to extracellular environment

Cell Bio (11 decks)

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