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Cells to Organisms 2 > Cell Adhesion 2 - Adhesion to the ECM > Flashcards

Cell Adhesion 2 - Adhesion to the ECM Flashcards

1
Q

is adhesion to the ECM permanent?

A
  • no
  • as cells need to migrate
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2
Q

What are integrins?

A
  • connect the cell to the ECM
  • heterodimers
  • transmembrane proteins
  • one end connects to fibronectin which connects to ECM
  • other end attaches to adaptor proteins which attach to actin (cytoskeleton)
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3
Q

Why is integrin connected to the cytoskeleton?

A

without this connection it would be flimsy

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4
Q

What is fibronectin?

A
  • dimer connected by disulphide bridge
  • cell attachment site - where integrins attach
  • ECM binding site - where collagen binds
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5
Q

What is the structure of integrin?

A
  • heterodimer
    • alpha sub-unit
    • beta sub-unit
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6
Q

What is the innactive conformation of integrin?

A

folded

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7
Q

What is the active conformation of integrin?

A
  • stretched
  • when bound to fibronectin
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8
Q

Explain integrin regulation

A

inactive - folded
active - stretched

  • reversible change - allows cells to move across ECM
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9
Q

How many different kinds of integrin do humans have?

A

24

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10
Q

how do integrins coordinate cell movement?

A
  • new attachments made at front of cell
  • old adhesions released at the back
  • actin forms bonds with ECM in direction of movement and releasing them at the back
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11
Q

What is the role of collagen in the ECM?

A

tensile strength - resist stretching

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12
Q

What is the role of glycosaminoglycans (GAGs)

A
  • resist compression - opposite of collagen
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13
Q

What is the structure of proteoglycans?

A

glycosaminoglycans (GAGs) join to core protein

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14
Q

How do glycosaminoglycans resist compression?

A
  • GAGs are negative
  • attract cations in the ECM
  • draw in water
  • swelling pressure
  • resisting compression
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15
Q

how do collagen and GAGs work together in the ECM?

A
  • tension in collagen
  • balanced by GAG swelling
  • resulting matrix is tough and resistant to pressure
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16
Q

Name a body part glycosaminoglycans are common?

17
Q

Are GAGs hydrophilic or hydrophobic?

A

hydrophilic
- space fillers in connective tissue

18
Q

What are others functions of proteoglycans?

A
  • binding growth factors
  • controlling migration of cells through ECM
19
Q

Explain tissue specific ECM composition

A

dense connecting tissues (tendon and bone) -> les GAG, more collagen. CaPO4 crystals in bone
vitreous humour -> made almost entirely of GAG, very little collagen

20
Q

What is an epithelium?

A

a sheet of cells joined together side by side. It covers all external surfaces and lines all internal cavities

21
Q

What are 4 different forms of epithelia and their functions and where you would find them?

A

columnar - secretion / absorption - intestinal lining

cuboidal - secretion / absorption - lining of kidney tubules

squamous - filtration - lining of lung

stratified - protection - epidermis of the skin

22
Q

What is the basal lamina?

A
  • thin tough sheet of ECM
  • separates epitaxial cells from collagen fibres in connective tissue
23
Q

where’d epithelial cells sit?

A

on the basal lamina

24
Q

What is the structure of the basal lamina?

A
  • type IV collagen and laminin
  • collagen supplied by underlying stromal cells (connective tissue)
  • laminin is supplied by overlying epithelial tissue
25
Q

What are stromal cells?

A

mesenchymal cells that make connective tissue

26
Q

What are mesenchymal cells?

A

Cells that differentiate into connective tissue

27
Q

What is the structure of laminin?

A

heterotrimers made of 3 sections

28
Q

What is the role of laminin?

A
  • interacts with proteins such as integrin
  • provides adhesive sites for integrins located in the basal membrane of epithelial cells
  • does a similar job to fibronectin in the connective tissue
29
Q

Explain epithelial polarity

A

two faces:
- apical - exposed to the lumen, air and bodily fluids
- basal - connected to the basal lamina

30
Q

Explain epithelial polarity in the gut

A
  • absorptive epithelial cells
  • secretory goblet (mucous) epithelial cells
  • different functions in same epithelial sheet
  • cells are polarised
31
Q

What are tight junctions?

A
  • segregate membrane proteins
  • prevents membrane proteins moving around the cell, maintaining its polarity
32
Q

What is the role of tight junctions in epithelial sheets?

A
  • allows them to function as barriers
  • binds epithelial cells to prevent leakage
33
Q

How has the role of tight junctions in epithelial cells been proven?

A
  • extracellular tracers stopped by tight junctions
34
Q

What forms tight junctions?

A
  • occluding
  • claudin
35
Q

Explain the role of tight junctions in the gut

A
  • Na+ active transport of glucose from the gut lumen
  • passive transport into the bloodstream
  • tight junctions prevents two transporters moving around the cell, maintaining polarity

Cells to Organisms 2 (26 decks)

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