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PHSL 233 > L9 > Flashcards

L9 Flashcards

1
Q

what are the 4 structures that hold epithelial cells together

A

tight junctions

adhering junctions

jap junctions

desmosomes

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2
Q

what is the role of microvilli

A

to increase the surface area

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3
Q

what is the role of the basement membrane

A

it is a supporting cushion for epithelial cells to sit on

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4
Q

what is the composition of the lipid bilayer

A

75% phospholipids
20% cholesterol
5% glycolipids

there are also very small amounts of other lipids

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5
Q

where does cholesterol sit in the membrane

A

it doesn’t have a hydrophobic head region therefore it sits deep in the membrane

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6
Q

what is an example of a glycolipid and what is it involved in

A

GPI is involved in protein trafficking

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7
Q

what are some of the roles that other lipids could have in the membrane

A

cell signalling and trafficking

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8
Q

what are the 2 different types of proteins in the lipid bilayer

A

internal membrane proteins and peripheral membrane proteins

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9
Q

describe internal membrane proteins

A

these span the entire lipid bilayer

eg Na and K channles

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10
Q

describe peripheral membrane proteins

A

these dont span the entire lipid bilayer. they are found inside the cell attached to internal membrane proteins

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11
Q

are the membranes static

A

no

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12
Q

what is the mosaic model of the lipid bilayer

A

Lipid molecules can move
sideways in their own half of the bilayer.

Proteins such as channels,
transporters, receptors, extracellular matrix proteins
etc are embedded in the lipid bilayer, but can also move within the bilayer (eg they can move along it

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13
Q

why is the mosaic model possible

A

because the bilayer is very flexible and dynamic for changing protein and lipid populations, cell growth, secretion and self sealing

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14
Q

what is the basement membrane

A

an extracellular matrix structure

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15
Q

what is the order in which you would find joining structures of the epithelial cells going from most apical to basolateral

A

tight junctions

adhering junction

desosomes

gap junctions

hemidesmosomes

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16
Q

what are some characteristics of the basolateral membrane

A

it is thin, flexible but tough and prevents cell movement

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17
Q

where are the proteins needed for the basolateral membrane secreted from

A

epithelial cells

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18
Q

what is epidermolysis bullosa

A

it is caused by collagen malfunctions so the anchoring of skin epithelial to the basement membrane (through hemidesmosomes) fails and blistering occurs

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19
Q

Patients presenting with epidermolysis bullosa present with severe blistering

BECAUSE

collagen dysfunction prevents proper anchoring of basement membrane to the epithelial cell

A

both are true and related

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20
Q

what are the 3 main functions of tight junctions

A

they act as a

barrier

gate

fence

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21
Q

how do tight junctions acts as a barrier

A

they limit passage of ions and molecules between cells in the parracleeulat pathway (between cells)

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22
Q

how do tight junctions acts as a gate

A

they allow certain solutes to flow through the paracellular pathway

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23
Q

how do tight junctions acts as a fence

A

they prevent the movement of proteins between the apical and basolateral domains

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24
Q

what is the importance of tight junctions acting as a fence

A

it helps to maintain the basal and apical polarity

these membranes need to be different because this is what makes epithelial cells epithelia

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25
Q

and tight junctions continuous or random

A

tight junctions sit close to the apical membrane and form a continuous structure

26
Q

how does the continuous tight junction form

A

it is formed by stands of claudin proteins linked to lipid bilayers to 2 cells pulling them together

27
Q

what structures are found in tight junctions

A

JAMs

claudin

occludin

28
Q

what is the role of JAMs, claudin and occludin

A

They all connect to proteins called ZO proteins. They then connect to the actin cytoskeleton which is what holds the tight junctions in place

29
Q

are all tight junctions the same

A

no

30
Q

what is the only structure in the tight junction that changes and how many different types are there

A

claudin and there are 27 types

31
Q

if a tight junction contains claudin 1 what characteristics will the tight junction have

A

no transport of ions/water molecules through the paracellular pathway

32
Q

where would tight junctions containing cludin 1 be located

A

in the skin and glomerulus

without them in the skin water would just seep out of us therefore we would die without it

33
Q

what are the characteristics of tight junctions with claudin 2

A

allows for transport of main ions and water through the paracellular pathway

34
Q

where would tight junctions containing cludin 2 be located

A

in the intestinal crypts and the proximal renal tubule

35
Q

what are the different names for the adherens junctions

A

zonular adherens

36
Q

what structure do multiple zonular adherens form

A

a belt structure just below the tight junctions

37
Q

what is the adherence belt made up of

what filament

A

actin filaments. it is the CAMs that being the 2 epithelial cells close together

38
Q

formation of adherens junctions initiates what

A

epithelia formation

39
Q

what is E cadherin

A

CAM

E stands for epithelial

40
Q

explain how E cadherin is related to cancer

A

E cadherin is important with cancers, breast cancer is an epithelial cancer. As it progresses the Ec loos the epithelial characteristics. This new cell is called mesenchymal. Then the epithelial cells becomes mesenchymal they are able to metastasise

The key part that drives this change is the loss of E cadherin causing the loss of formation of these adherence’s junctions causing the epithelial cells to become disorganised. When this is what allows the cells to brake off and get into the blood streem and metastasis

The cadherins bring the cells together and then these are held in place by anchor proteins from the epithelial cell. These proteins are attached to the actin cytoskeleton

41
Q

describe the characteristics of desmosomes

A

These hold epithelial cells together in single spots (not continuous)

They brings cells together through desmosomal cadherins

These are the anchor point for intermediate filaments which are part of the cytoskeleton which is made of keratin

42
Q

where are hemidesmosomes found

A

joining the basal lamina to epithelial cells

43
Q

what do hemidesmosomes consist of

A

they are keratin (intermediate) filaments which are embedded in a plaque and joined via the protein plectin to integrins

44
Q

what is the role of the integrins (in relation to hemidesmosomes)

A

Integrins help to integrate the hemidesmosomes to the basal laminar

45
Q

what are gap junctions

A

they are tiny channels between cells made of connexin proteins

the permit regulated passage of ions and small molecules

not continuas they are in single spots

46
Q

what is the difference between a connexin and a connexon

A

connecOn = a group of six connexIns

47
Q

how small do molecules need to be to move through gap junctions

A

< 1000 Da

48
Q

what forms a channel

between 2 cells

A

when a conexon on one epithelial cell lines up with a conexon on another epithelial cell

49
Q

what are the 3 main cytoskeletal types

A

actin filaments

intermediate filaments

microtubules

50
Q

what does actin do in the cytoskeleton

A

it determines cell shape and dives the movement of cells therefore playing a role in cancer migration

51
Q

what is the role of intermediate filaments

A

provide mechanical strength and resistance to shear stress (Eg when the wind blows your hair up (when its parallel to your head).

52
Q

what is the role of microtubules

A

to position agranells, railroads for intracellular vesicle transport, form the mitotic spindle and is the motile component of cilia

53
Q

what is an important feature of the cytoskeleton

A

that it is dynamic and able to adapt to internal and external signals

54
Q

what is the role of accessory proteins in the cytoskeleton

A

to regulate the assembly and disassembly of things

they also link other structures together

55
Q

what do actin filaments consist of

A

2 stranded helical polymers of actin

56
Q

what is the role of myosins in actin filaments

A

they are motor proteins that bind to actin filaments and use ATP for contraction, transport proteins, vesicles and organelles along that actin filaments

57
Q

what are microtubules made of

A

alpha and beta tubulins

58
Q

what are microtubules needed for

A

cell motility, division and vesical movement

59
Q

what are kinesin and dynein in relation to microtubules

A

they are molecular motors that allow transport of vesicles and organelles around the cell using ATP

they are accessory proteins

60
Q

Desmosomes connect epithelial cells to the basement membrane

BECAUSE

the basement membrane consists of extracellular matrix proteins

A

the first is false (should be hemidesmosomes) and the second is true

PHSL 233 (31 decks)

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