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BIO130 > Week 11 - Interactions Between Cells and Their Environment (Junctions and Adhesion) > Flashcards

Week 11 - Interactions Between Cells and Their Environment (Junctions and Adhesion) Flashcards

1
Q

Cells interact with each other in the ECM to form what?

A

To form tissues.

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2
Q

What are the 4 major ways of cell interaction?

A
  1. Anchoring junctions
  2. Occluding junctions
  3. Channel-forming junctions
  4. Signal-relaying junctions
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3
Q

Which 3 junctions are present in epithelial cells?

A

Anchoring, occluding, and channel-forming junctions.

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4
Q

In polarized epithelial cells, how are junctions arranged?

A

They are arranged in a specific order.

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5
Q

What is a polarized epithelial cell?

A

It is a mature epithelial cell.

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6
Q

On epithelial cells, what sides are junctions usually on?

A

They can be on the basal or lateral side; but most are on the lateral side, discussed as “relatively” apical/basal for visualization and location descriptions.

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7
Q

What kind of junction is a Tight junction?

A

An occluding-junction.

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8
Q

What do tight junctions do?

A

They block anything from going between the cells and keep proteins on their correct sides.

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9
Q

Where are tight junctions relatively located on epithelial cells?

A

They are the apical-most junction; not in one single spot, but all along the region between 2 cells.

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10
Q

What do tight junctions all along the region between 2 cells form?

A

Form a “sealing strand”, a.k.a. Tight Junction Belt.

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11
Q

What kind of junction is an Adherens junction?

A

An anchoring junction.

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12
Q

What do Adherens junctions do?

A

They anchor 2 cells together.

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13
Q

Where are Adherens junctions relatively located on epithelial cells?

A

They are more basal than Tight junctions; all along the region between 2 cells.

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14
Q

What do Adherens junctions all along the region between 2 cells form?

A

Form an “Adhesion Belt”.

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15
Q

What kind of junction is a Desmosome?

A

An anchoring junction.

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16
Q

What do desmosomes do?

A

They anchor a cell at a PARTICULAR spot.

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17
Q

Where are Desmosomes relatively located on epithelial cells?

A

They are more basal than Adherens junctions.

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18
Q

What kind of junction is a Gap junction?

A

A channel forming junction.

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19
Q

What do Gap junctions do?

A

They form and act as channels.

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20
Q

Where are Gap junctions relatively located on epithelial cells?

A

Gap junctions are the basal-most junction.

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21
Q

What kind of junction is a hemi-desmosome?

A

An anchoring junction.

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22
Q

What do hemi-desmosomes do?

A

They anchor a cell to the Extracellular Matrix (ECM).

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23
Q

Where are hemi-desmosomes relatively located on epithelial cells?

A

They are ON the basal face; a half-circle kind of shape.

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24
Q

The tight seal created by tight junctions prevent mixing of what 2 things?

A
  1. Extracellular environments

2. Membrane proteins

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25
Q

What 2 proteins for the tight seal of Tight junctions?

A
  1. Claudin

2. Occludin

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26
Q

Claudin/Occludin are required for what?

A

For tight junction seals.

27
Q

The extracellular domains of transmembrane proteins interact with what?

A

Interact with the extracellular domains of neighbouring cell’s proteins.

28
Q

Proteins forming tight junction seals interact in what style?

A

Homotypic style reaction: Occludin with occludin, claudin with claudin.

29
Q

Tight junctions are dependant on what other kind of junction?

A

Dependant on Adherens junctions.

30
Q

If you block the formation of adherens junctions, what happens to tight junctions?

A

Tight junctions do not form properly.

31
Q

What 3 junctions for the Junctional Complex of epithelial cells?

A
  1. Tight junctions (TJ)
  2. Adherens junctions (AJ)
  3. Desmosomes (D)
32
Q

Occluding-junctions can provide a bit of mechanical strength, but not as much as which other kind of junction?

A

Not as much mechanical strength as anchoring junctions.

33
Q

What are 3 examples of anchoring junctions?

A
  1. Adherens junctions
  2. Demsosomes
  3. Hemidesmosomes
34
Q

What links cytoskeletal filaments on neighbouring cells?

A
  • adhesion proteins
  • transmembrane proteins
  • anchor proteins
35
Q

Intracellular domains of adhesion proteins interact with what?

A

Interact with anchor proteins.

36
Q

Extracellular domains of adhesion proteins interact with what?

A

Interact with neighbouring adhesion proteins and the extracellular matrix.

37
Q

What do anchor proteins link?

A

They link adhesion proteins to cytoskeletal filaments via cytosolic proteins.

38
Q

What does the adhesion belt encircle?

A

It encirclrs the inside of the plasma membrane.

39
Q

What 2 “proteins” work at Adherens junctions?

A
  1. Cadherin proteins

2. Actin

40
Q

What do Cadherin junctions do at Adherens junctions?

A

They are transmembrane proteins that help neighbouring cells interact with each other.

41
Q

What does Actin do at Adherens junctions?

A

Actin is tethers to cadherin by anchor proteins.

42
Q

Why do cells sort themselves into layers? (2 reasons)

A
  1. Different cadherin proteins are expressed in each cell type
  2. Cadherins form homotypic junctions
43
Q

What do desmosomes and hemidesmosomes link?

A

Link intermediate filaments, which provide the most structural strength.

44
Q

Where do hemidesmosomes link filaments?

A

The link is to the basal lamina, or other parts of the ECM.

45
Q

What are the 2 adhesion proteins that form Desmosomes?

A
  1. Desmoglein

2. Desmocollin

46
Q

What 2 anchor proteins link the adhesion proteins to intermediate filaments?

A
  1. Plakoglobin

2. Desmoplakin

47
Q

What are Gap junctions composed of?

A

Composed of connexin proteins; making connexon.

48
Q

What does a connexon consist of?

A

6 connexin proteins.

49
Q

In what 2 ways do gap junctions couple cells?

A
  1. Electrically

2. Metabollically

50
Q

What 4 molecules WILL pass through a gap junction?

A
  1. cAMP
  2. nucleotides
  3. glucose
  4. amino acids
51
Q

What 3 things will NOT pass through gap junctions?

A
  1. macromolecules
  2. proteins
  3. nucleic acids
52
Q

One connexon (hemichannel) on it’s own is usually what?

A

Usually closed.

53
Q

A dramatic increase in cytosolic Ca2+ will do what to gap junctions?

A

It will close gap junctions.

54
Q

Cytosolic Ca2+ is usually what?

A

Usually low in concentration.

55
Q

What happens at gap junctions when there is membrane damage?

A
  • Ca2+ leaks into the cell and concentration is abnormally high
  • metabolites leak out
56
Q

If gap junctions remain open, and one cell gets damaged, what happens to the connected cell?

A

It also gets damaged.

57
Q

What 2 things is the plant cell wall composed of?

A
  1. Cellulose

2. Pectin

58
Q

What is plasmodesmata?

A

Plasmodesmata are junctions between plant cells.

59
Q

How are 2 plant cells connected by the plant cell wall?

A
  • plasma membrane is shared; they share phospholipids, transmembrane proteins, etc.
  • they exchange extracellular fluid
  • ER extends and forms into other cell’s ER; share organelles
60
Q

What is the basement membrane of epithelial cells?

A

Underneath epithelial cells; basal lamina.

61
Q

What is underneath the basal lamina of epithelial tissue?

A

Connective tissue.

62
Q

Connective tissue vs. Epithelial tissue.

A 
Connective: 
- cells rarely connected 
- plentiful ECM 
- ECM provides resistance to mechanical stress 
- cells attatched to the matrix
Epithelial:
- cells closely associated 
- limited ECM 
- cytoskeletal filaments provide resistance to mechanical stress
- cells attatched to eachother
63
Q

What makes up the Extracellular Matrix (ECM) and some functions?

A
  • connective tissues (composed of fibrous proteins)
  • different compositions give tissues different protperties
  • ECM remodeled over time

BIO130 (12 decks)

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