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BIO230 Section 2 > 2.3: Cell Adhesion > Flashcards

2.3: Cell Adhesion Flashcards

1
Q

cell __________ and __________ is essential for multicelllular organisms

A

polarization, cohesion

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2
Q

polarized cells can? (3)

A
  • define inside vs outside
  • have diff functions at diff cell regions
  • transmit signals
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3
Q

how is mechanical stress transmitted from cell to cell in epithelial tissues

A

by cytoskeletal filaments anchored to cell-matrix and cell-cell adhesion sites

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4
Q

the extracellular matrix directly bears what type of stress (and 2 types of this specific stress)

A

mechanism: tension and compression

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5
Q

what is connective tissue made up of

A

collagen fibers, ecm, cells kinda spaced far apart

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6
Q

many animal cells are either connective or epithelial tissue, what are these?

A

epithelial tissue: cells directly connected to each other w minimal ecm (basal lamina sometimes considered part of epithelial tissue)
connective tissue: cells dispersed through ecm

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7
Q

state what epithelial cells line and provide examples

A

surfaces: protective epithelial cell layers on the surface of the organism (skin)
cavities: absorptive epithelial cells lining a cavity of the organism (digestive tract)
organs: epithelial cells surrounding and defining organs

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8
Q

t/f are lining patterns consistent

A

true

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9
Q

t/f are epithelial cells polarized and explain how

A

true. each cell surface must be different to perform different functions, these cell surfaces define the inside vs outside of the organism or tissue

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10
Q

list the junctional complexes of (mature) epithelial tissues from apical to basal

A

tight junction, cell-cell anchoring junction, channel forming junction, cell-matrix anchoring junctions

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11
Q

define tight junctions

A

seals gap between epithelial seals. all along the region between two cells, makes sealing strands

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12
Q

the order of junctional complexes from apical to basal are distinct, are these the same in all cells

A
  • mature cells definitely have junctions and in that order
  • other cells may or may not have all of them or in that order (case to case dependent)
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13
Q

what makes sealing strands and what makes adhesion belts

A

tight junctions make sealing strands and adherens junctions make adhesion belts

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14
Q

define adherens junction

A

connects actin filament bundle (apart of cytoskeletal filaments) in one cell with that in the next cell. the actin anchors on that side of the cell and doesn’t go to other side, the adherens junction is all along region between two cells to form adhesion belts

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15
Q

define desmosome

A

desmosomes connects intermediate filaments (cytoskeletal filaments) in one cell to those in the next. desmosomes are just in that spot and don’t go to the other side.

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16
Q

define gap junctions

A

allows the passage of small water-soluble molecules from cell to cell (not with outside cell)

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17
Q

what does relative positioning mean in epithelial cells

A

it’s when there is greater presence of a junctional complex on the apical vs basal side - eg desmosomes more apical than gap junctions

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18
Q

what (2) types of junctional complexes connect the epithelial cell of the basal connective tissue underneath

A
  1. actin linked cell matrix junction: anchors actin filaments in cell to ecm
  2. hemidesmosome anchors intermediate filmaments in cell to ecm
    note that filaments don’t go outside (cytoSKELETAL stays inside)
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19
Q

which junctional complexes are considered cell cell junctions

A

adherens and desmosomes

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20
Q

which junctional complexes are considered cell-ecm junctions

A

actin linked cell matrix junction and hemidesmosomes

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21
Q

cell cell junctions are usually mediated by ____________ and cell-ecm junctions usually mediated by ___________ and cytoskeleton may be _______ or ____________ filaments

A

cadherins. integrins, actin or intermediate filaments
*cadherins is for adherin junctions and cadherin family is for desmosomes

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22
Q

what are intracellular adaptor proteins used for

A

they are inside the cell and they hold the transmembrane adhesion proteins while the other end of the tm prot either is cell-cell or cell-ecm

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23
Q

cadherins are tm proteins expressed by (one or both) cells - cadherins mediate cell-cell connections at adherens junctions

A

both (it’s like velcro)

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24
Q

cadherins interact (homophilic or heterophilic) interactions of their extracellular domains

A

homophilic - N terms of both connect
ie e cadherin can go w e cadherin but cannot go with n cadherin

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25
Q

cadherins interactions require what and what does it do

A

ca2+ - makes hinge regions rigid to help them stick together (think of wrists as the hinge in regards to arm)

26
Q

what is the result of homophilic cadherin interactions

A

cells expressing different cadherins sort into two separate groups that do not interact

27
Q

cadherins form homophilic interactions with their ec domains to directly link _____________ and indirectly interact with __________-_

A

adjacent cells, actin filaments

28
Q

do cahrerins act directly or indirectly with actin filaments, and what is the result

A

indirectly ==> these interactions indirectly link the actin cytoskeleton between adjacent cells in epithelial tissues

29
Q

caherins interact in patches to form a strong _________ belt

A

adhesion

30
Q

adhesion belts can mediate ?

A

morphogensis

31
Q

describe morphogenesis by adhesion belts

A

the sheet of epithelial cells can undergo invagination caused by an organized tightening of adhesion belts in selected regions of the cell sheets (the actin contracts = tightening = shape forming) -> epithelial tube pinches off from overlying sheets of cells -> then it can become a shape eg the epithelial tube

32
Q

t/f you need the correct cadherins to create specific shapes through morphogenesis

A

true

33
Q

in an ectoderm, cells express different cadherins to establish new interactions and ensure the closure of which feature

A

neural tube closure (the neuron tube is joined by a different cadherin that made up the original ectoderm and the original cadherin that makes up the neural tube)

34
Q

cell adhesion is essential for which 2 processes

A

embryo development (must adhere properly so when the cells move itll be coordinated movements to separate head from a foot yk) and morphogenesis

35
Q

Which of the following most closely resembles adherens junctions
mutations in the outer epithelium of Drosophila embryos?
a) Hemidesmosome mutation in the outer epithelium.
b) Calcium removal at the outer epithelium.
c) Intermediate filament depolymerization in the outer epithelium.
d) Occludin mutation in the outer epithelium.

A

B.
A is wrong bc if doesn’t resemble. B is right be we need calcium to make it rigid so no calcium will make it flimsy thus the embryo won’t develop properly. C is wrong bc it’s not intermediate filaments, I think it’s actin (double check). D is wrong bc occludin is for tight junctions.

36
Q

tight junction define the _____ of the cell

A

domains - they separate apical and basal

37
Q

state what the apical and basal domain face

A

apical - surface, cavity, organ
basal - inside of the body

38
Q

occludins and claudins form ___________ and these form ________ strands

A

tight junctions == sealing strands
* many rows of these proteins are needed to form a functional tight junction

39
Q

claudin and occludin are tight junction proteins with how many passes into the TM

A

4

40
Q

occludins and claudins for homo or heterophilic interactions with their ec domains to directly link adjacent cells

A

homophilic

41
Q

is linking of adjacent cells by tight junctions direct or indirect

A

direct

42
Q

tight junctions limit diffusion into the __________ space and limit the diffusion of what

A

extracellular, membrane proteins

43
Q

membrane proteins can or cannot diffuse in the plasma membrane

A

can

44
Q

which junctional complex prevent membrane proteins from moving between the apical and the basolateral domains

A

tight junctions

45
Q

explain how tight junctions regulate what enters an organism (in the example of absorbance of glucose from the intestinal lumen)

A
  • tight junctions function to stop anything from directly diffusing from the gut lumen into connective tissue and blood
  • active transporters (Na+ driven glucose transporter) must move glucose into the epithelial cell on the apical domain from the gut lumen (low C gluc bc keeps being moved into cell)
  • passive carriers (passive glucose transporter) in the basolateral domain allow glucose to diffuse out of the epithelial cell into the connective tissue/blood
  • tight junctions keep the correct transporters in their correct domains of the cell
46
Q

in the absorbance of glucose from the intestinal lumen, state the 2 relevant transporters and which domain they are in

A

na+-driven glucose transporter (active) in the apical
passive glucose transporter (passive) in basolateral

47
Q

_______________ mediate cell to cell matrix junctions

A

integrin heterodimers

48
Q

integrins directly or indirectly interact w actin filaments

A

indirectly

49
Q

cell matrix junctions play roles in both epithelial and connective tissues, define these both

A

epithelial tissue: adhesion to the basal lamina ecm
connective tissue: cell interaction iwth the ecm and cell movement

50
Q

what are polarity cues

A

signal to make ends different, these can establish cell cohesion

51
Q

what is cell cohesion established by

A

polarity cues

52
Q

describe how polarity cues can establish cell cohesion and examples

A
  • adherens junctions form first, this is the primary landmark –> subsequent elaboration
  • adherens junctions provide polarity cues to define apical from basolateral domains for epithelial cells (the first polarity cue defines the rest)
  • tight junctions form apical to the adherens junctions-after the separation of apical and basolateral

example: adherens junction cause the polarity cues of par and crumbs to dictate the apical domain. it inhibits scribble (polarity cue) which creates the basolateral domain

53
Q

t/f only epithelial cells use the polarity cue systems

A

no, all cells

54
Q

state what an initial landmark (can be strucutre, prot, signal, or process) generate

A

subsequent patterns

55
Q

describe how ec signals can polarize cell behaviour in regards to rac and rho

A

on neutrophils, the chemoattractant acts on the receptor which is the primary landmark that indicates rac (polymerization (- protrusion)) to go towards and rho to go away (actin-myosin contraction)

56
Q

t/f cell polarity can be established external OR internal signals

A

true

57
Q

describe how external signal (sperm entry) can establish cell polarity

A

the initial polarity signal was external (sperm entry) which is the primary landmark. asymmetric cell division can unevenly distribute internal polarity cues between child cells – defining the anterior and posterior through the rho gef gradient.

58
Q

An occludin mutation in ________ cells will directly affect __________.
a) intestinal epithelial; glucose transport.
b) Drosophila embryonic; movement of the outer epithelium.
c) Drosophila embryonic; segmentation of the outer epithelium.
d) epithelial; adherens junction formation.

A

A.
B is wrong bc movement is for cadherin. C is wrong bc we don’t even know segmentation. D is wrong bc if adherens it’s a whole separate thing and they form before tight junctions

59
Q

list the 3 key components of cell polarity to define a functional epithelium

A

intracellular trafficking, cytoskeleton organization, cell cohesion

60
Q

what does a functional epithelium define

A

organs and organisms by separating proteins on sides and keeping them there

BIO230 Section 2 (12 decks)

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