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Cell Biology > Module 8 > Flashcards

Module 8 Flashcards

(46 cards)

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1
Q

what is multicellularity?

A

stable interactions between cells

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2
Q

what is he ICM?

A

the early embryo that eventually separates into 3 germ layers

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3
Q

what are the 3 germ layers?

A

ectoderm
mesoderm
endoderm

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4
Q

what are CAMs?

A

Cell adhesion molecules, these are transmembrane proteins that are required for recognition and contact between cells

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5
Q

what are the different types of epithelial cell junctions?

A
  1. tight junctions
  2. adherens junctions
  3. desmosomes
  4. hemidesmosomes
  5. gap junctions
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6
Q

what is the difference between apical and basal surfaces of cells?

A 
apical = top
basal = bottom
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7
Q

what do tight junctions connect?

A

connect adjacent epithelial cells below the apical surfae and completely seal off the space between cells to prevent fluid movement

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8
Q

why must there be no fluid movement between cells of a tight junction?

A

I) to restrict diffusion of small molecules

II) prevents leakage of digestive enzymes

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9
Q

what proteins are closely arranged in tight junctions?

A

occludin and claudin proteins are closely arranged between the cells

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10
Q

true or fales: diffusion is limited at tight junctions

A

true, the molecules should NOT be able to move much

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11
Q

what do gap junctions connect? what does this do?

A

they directly link to cytosol of one cell to another

this integrates metabolic activities

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12
Q

what can be exchanged between cells at a gap junction?

A

ions
small molecules
secondary messengers (cAMP, Ca2+)

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13
Q

what are examples of secondary messengers?

A

cAMP

Ca2+

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14
Q

what is a hemichannel?

A

this is a channel seen at gap junctions
that are made of 6 connexin subunits
they are found in groups

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15
Q

how many hemichannels make a gap junction?

A

two of them but they are found in groups

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16
Q

in what cases in the human body are gap junctions useful?

A

they allow coordination of cardiac muscles and uterine muscles

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17
Q

what type of junctions do plasmodesmata resemble?

A

gap junctions but in plant cells

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18
Q

what is a phloem and why are plasmodesmata important for them?

A

a phloem is a system of elongated tubes formed in linear arrays of connected cells which carries nutrients from the leaves to the rest of the plant
the plasmodesmata are important structures to the phloem

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19
Q

what are companion cells?

Study These Flashcards
A

they are plant cells that are associated with their development and function
I) they provide ATP proteins and other substances to the sieve-tube elements
II) they are connected to the cells of the phloem

20
Q

what is the plants circulatory system?

Study These Flashcards
A

the phloem that carries sucrose to the rest of the plant

21
Q

what macromolecules are communicated through plasmodesmata?

Study These Flashcards
A

I) transcription factors
II) gene transcripts
III) small RNAs

22
Q

what are anchoring junctions?

Study These Flashcards
A

I) adherens junctions
II) desmosomes
III) hemidesmosomes
they associate with the cytoskeleton by actin filaments

23
Q

what is an adherens junction?

Study These Flashcards
A

this is a type of anchoring junction that connect the actin cytoskeleton between neighboring cells

24
Q

what is the difference between desmosomes and hemidesmosomes junctions?

Study These Flashcards
A

they are both types of anchoring junctions

desmosomes: links two cells together
hemidesmosomes: attach one cell to the extracellular matrix

25
what kind of CAMs make up the adherens junctions?
1. cadherins 2. Ig-superfamily 3. integrins 4. selectins
26
what is the difference between homophilic interactions and heterophilic interactions?
homophilic interactions = association of similar cells | heterophilic interactions= association of different cells
27
what are the different classes of cadherins?
1. E-Cadherin 2. N-Cadherin 3. P-Cadherin
28
what are cadherins? what do they do?
they are Ca2+ dependent CAMs that mediate HOMOphilic interactions they mediate epethelial cell-cel adhesion near the apical surface of the cell right below tight junctions
29
what anchors cadherins to the actin cytoskeleton?
1. multiprotein complexes that involve the transmembrane cadherins 2. cytosolic co-factors known as cantenins
30
what do cantenins do?
anchor cadherins to the actin cytoskeleton
31
what do E-cadherins do?
they mediate Ca2+ dependent adhesion of epithelial cells
32
what are the 5 stages of extravasation? explain them.
1. Capture of Leukocyte - mediated by cytokines that are released at the site of infection (TNF-alpha cytokine) - a receptor on the basal surface of the cell receives the signal that triggers the release of P-selectins on the apical surface of the cells - this allows the P-selectin to interact with their ligand, a glycoprotein on the surface of the leukocyte 2. Rolling - as the neutrophils are pushed over the surface of the endothelial cells while establishing and losing transient connections with the apical surface 3. Slow rolling - as the neutrophil gets closer to the site of infection the density of selectins at the surface of the epithelial cells increase - endothelial cells at the site of infection now display both P-selectins and E-selectins, the increase of interactions further slow down the rolling 4. Firm adhesion - now PAF can interact with the PAF receptor on the neutrophil - at this stage integrins are activated, which allows interaction with iCAMS and further slows movement 5. Transmigration - here the neutrophil is no longer moving and it is able to crawl through the cells at the site of infection - the connections between endothelial cells have been broken by enzymes
33
what triggers extravasation?
infection
34
what is a leukocyte?
a type of white blood cell that helps the body combat infection
35
what are the 3 types of leukocytes?
I) granulocytes - target pathogens - include: neutrophils, eosinophils, basophils - neutrophils most numerous and target bacterial infections - only neutrophils undergo extravasation II) Monocytes - differentiate into macrophage that engulf the bacterial invading cells - undergo extravasation III) Lymphocytes - include NK cells (natural killer) that lyse virally infected cells and tumour cells - T and B cells produce antibodies as part of their immune response and can also undergo extravasation
36
true or false: all granulocytes undergo extravasation
FALSE, only neutrophils, not eosinophils or basophils
37
what type of leukocytes can undergo extravasation?
- neutrophils - monocytes/macrophage - T and B cells
38
what is the ligand of a P-selectin?
a glycoprotein on the surface of the leukocyte cell
39
where are the P-selectins?
on the apical surface of the endothelial cell
40
what is PAF?
this is a membrane-anchored cytokine on the endothelial cell that comes into play during firm adhesion (step 4) of extravasation of a leukocyte in response to an infection.)
41
what are examples of neutrophil cytokine receptors?
CXCR1 | CXCR2
42
true or false: ligand binding to PAF receptors can only occur if the cells are not slow rolling
FALSE, ligand binding to PAF receptors can only occur if the cell IS undergoing slow rolling
43
describe integrin activation
integrin becomes active as a result of PAF signalling once active the integrin can now bind to iCAMs on the endothelial cell ALSO, integrin activation changes neutrophil behaviours such as the reorganization of the cytoskeleton to allow cell migration
44
which is stronger: the interaction between integrins and their ligands of selectins and their ligands?
the interaction between integrins and iCAMs
45
true or false: integrins are activated before selectins
FALSE, selectins are activated BEFORE integrins
46
describe the inactive state of integrin
the beta-A-domains are folded down - these domain form the ligand-binding domain and therefore render the integrin inactive - PAF signalling will change the conformation of these domains

Cell Biology (4 decks)

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