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MBB 231 > Lecture 24 - Interactions Between Cells and Their Environment > Flashcards

Lecture 24 - Interactions Between Cells and Their Environment Flashcards

1
Q

def: a collection of structurally similar cells that cooperate tp perform a specific function

A

tissue

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2
Q

where did all the proteins outside a cell originally come from?

A

inside the cell

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3
Q

what are the 3 roles of the ECM?

A
  1. helps determine cell shape
  2. provides physical support for cells
  3. plays a regulatory role in cell signalling
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4
Q

what are the 3 types of extracellular matrix?

A
  1. bone
  2. cartilage
  3. connective tissue
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5
Q

def: hard calcified ECM that contains a small number of interspersed cells

A

bone

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6
Q

def: cells are imbedded in a flexible ECM rich in proteoglycans

A

cartilage

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7
Q

def: gelatinous ECM surrounding glands and blood vessels

A

connective tissue

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8
Q

def: structural proteins that provide strength and flexibility

A

collagens/elastins

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9
Q

def: components of hydrated matrix

A

proteoglycans

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10
Q

def: adhesive/connective glycoproteins that allow cells to attach to the ECM

A

fibronectin/laminins

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11
Q

what is the most abundant protein in the human body ?

A

family of closely related collagens, which form fibres with high tensile strength

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12
Q

collagen is secreted by several types of cells in connective tissues including __________-

A

fibroblasts

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13
Q

def: mutations in collagen resulting in the excessive looseness of skin and joints

A

ehlers-danos

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14
Q

def: a temporary collagen disease, because vitamin C is a co-factor in collagen synthesis

A

scurvy

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15
Q

all collagens occur as a ________, with rigid triple helix of intertwined polypeptides, _______ chains

A

trimer, alpha

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16
Q

collagens are very rich in:

A

glycine, proline and lysine

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17
Q

no vitamin C results in what in terms of collagen?

A

no hydroxyls can be added which means weaker interactions

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18
Q

def: three alpha chains assemble to form a triple helix, with short non-helical sequences at both ends

A

procollagen

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19
Q

once procollagen is secreted out of the cell, what cleaves it and removes it from both ends of the molecule?

A

procollagen peptidase

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20
Q

collagen has tensile strength but not enough for some types of tissue, in these cases elasticity is provided by ________

A

elastins

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21
Q

def: rich in glycine and proline, molecules are cross-linked by covalent bonds between lysine residues

A

elastins

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22
Q

with time, what happens to elastins?

A

they’re lost from tissues and skin will wrinkle and joints are less flexible

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23
Q

def: meshed gel-like network of collagen and elastin fibers

A

proteoglycans

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24
Q

def: large carbohydrates with repeating disaccharide units

A

glycosaminoglycans (GAGs)

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25
Q

what are the most common types of GAGs?

A
  1. chondroitin sulfate
  2. keratan sulfate
  3. hyaluronate
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26
Q

the presence of charged sulphate and carboxyl groups attract ______, which bind water, creating a hydrated and gelatinous matrix

A

cations

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27
Q

most GAGs in the ECM are ___________ _________ ____________ to form proteoglycans

A

covalently bound to proteins

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28
Q

def: reinforce direct links between the ECM and the plasma membrane

A

adhesive glycoproteins

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29
Q

what are the most common adhesive glycoproteins?

A

fibronectins and laminins

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30
Q

what is the structural composition of fibronectin?

A

consists of 2 very large polypeptide subunits linked near the C-terminus by disulfide bonds

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31
Q

what do the functional units of fibronectin bind?

A
  1. numerous components of the ECM
  2. bind receptors on the cell surface
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32
Q

def: family of proteins with three subunits linked together by disulfide bonds

A

laminins

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33
Q

what can bind to the binding sites on laminins?

A
  1. collagen
  2. proteoglycans
  3. other laminins
  4. receptors on cell surfaces
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34
Q

where are laminins mainly found?

A

in the basal lamina as a thin sheet of specialized extra cellular material

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35
Q

integrins integrate the _____ and ______ cellular environments

A

extra- and -intra

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36
Q

what do integrins do outside the cell?

A

bind to a diverse array of molecules

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37
Q

what do integrins do inside the cell?

A

interact with dozens of different proteins to influence cellular events

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38
Q

what is the physically composition of integrins?

A

two large transmembrane polypeptides, an alpha and beta chain, which are non-covalently linked to each other

39
Q

how do integrins differ each other?

A

binding specificity, subunit size and tissue distribution

40
Q

where is the ECM binding site of an integrin?

A

the extracellular domains of the alpha and beta chains, right in the cleft between the chains

41
Q

what are the 2 confirmations of integrins and what do they correspond to?

A
  1. bent - inactive and cannot bind
  2. upright = active and ligand bound
42
Q

what does the intracellular domain of an integral do?

A

binds proteins like Talin, which separates the alpha and beta chains and activates the integrins

43
Q

what are the 2 types of activity integrins are impacted in ?

A

adehesion and signal transduction

44
Q

def: intracellular signalling can induce integrity clustering, which effect ECM binding

A

“inside out” signalling

45
Q

def: integrins can act as receptors that activate intracellular signalling cascades

A

“outside-in” signalling

46
Q

for most cells to grow in culture, they must be attached to ___________, if they can’t attach to an ECM layer, they will stop dividing

A

substratum

47
Q

def: the need to cells to be attached to a substratum in order to grow and divide, involves the activation of intracellular pathways following integral clustering at focal adhesion

A

anchorage dependent growth

48
Q

in vitro, anchorage dependent growth requires attachment of a cell to the substratum, this occurs in stages at discrete sites called _________ __________

A

focal adhesions

49
Q

how to integrins interact with actin microfilaments?

A

via linker proteins talin, vinculin, and alpha actinin

50
Q

def: the tightest attachment between a cell and its ECM occur at these special adhesive structures

A

hemidesmosomes

51
Q

where are hemidesomosomes found?

A

in epithelial cells, they contain integrins and attachch a cell to a substrate, like the basal lamina

52
Q

in hemidesmosomes, integrins are attached to the ________________ protein _______________

A

intermediate filament protein keratin

53
Q

the linker proteins in hemidesmosomes form _ ________ ________, connecting the integrins to the cytoskeleton

A

a dense plaque

54
Q

what are the 4 families of cell adhesion molecules? (CAMs)

A
  1. integrins
  2. catherins
  3. selectins
  4. Ig-superfamily
55
Q

which CAM has Ca2+ dependent binding?

A

cadherins

56
Q

which CAM has Ca2+ independent binding?

A

Ig-superfamily

57
Q

def: may be the most important proteins in molding cells into cohesive tissue and holding the tissue together

A

cadherins

58
Q

what are the physical properties of a cadherin?

A
  • small cytoplasmic domain
  • single membrane spanning domain
  • large extracellular component, consisting of 5 domains of similar size and strucutre
59
Q

what provides rigidity to the cadherin strucures, allowing them to zip together?

A

Ca2+ binding between the domains

60
Q

beta catenin and alpha catnenin bind to the ________ ________ of cadherin and that recruits actin to the membrane

A

cytosolic tail

61
Q

what are the 2 roles of catenin proteins?

A
  1. tethering the cadherin to the cytoskeleton
  2. transmitting extracellular signals to the cytoplasm and nucleus
62
Q

def: compound that binds to a specific carbohydrate group

A

selectin

63
Q

what is the physical composition of a selectin?

A
  1. small cytoplasmic domain
  2. single membrane spanning domain
  3. large extracellular component, consisting of a number of domains ending in the lectin-binding domain
64
Q

when a wall of a blood vessel receives a chemical signal that there is nearby damage, what happens?

A

activated endothelial cells display P-and E-selectins to “capture” a neutrophil that is rolling along the wall

65
Q

what part of the endothelial cell surface bind to the receptor on a neutrophil and triggers a signal cascade that activates integrins

A

the phospholipid platelet activating factor (PAF)

66
Q

what stops the rolling of a neutrophil?

A

the ICAM and integrins interacition

67
Q

what are the 3 common types of junctions within animal cells?

A
  1. adhesive junctions (adherens junctions and desmosomes)
  2. tight junctions
  3. gap junctions
68
Q

which cell junctions create adhesion points?

A

adherens junctions and desmosomes

69
Q

which cell junctions seal the space between cells?

A

tight junctions

70
Q

which cell junctions form communication ports between cells?

A

gap junctions

71
Q

what are adherens junctions made of?

A

CAMs and cadherins

72
Q

what are desmosomes made of?

A

CAMs and cadherins

73
Q

what are tight junctions made of?

A

occluding and claudins

74
Q

what are gap junctions made of?

A

connexins

75
Q

def: form a continuous belt that encircles the cell near the apical end of the lateral membranes, prominent in epithelial cells of the kidney

A

adherens junctions

76
Q

how big is the space left by adherens junctions?

A

30 nm

77
Q

adherens junctions are ___________ ____________ junctions that interact with _________________

A

cadherin-mediated, microfilaments

78
Q

def: disk-shaped points of strong adhesion between adjacent cells in a tissue, abundant in cells that experience mechanical stress

A

desmosomes

79
Q

def: extracellular space of 30 nm between the two connected cells

A

desmosome core

80
Q

desmosomes rely on _________ _________ _______ which indirectly interact with ____________ _________

A

desmosomal-specific catherine, intermediate filaments

81
Q

the beta-catenin family protein ___________ binds the cadherins, and the linker protein ________________

A

plakoglobin, desmoplakin

82
Q

what does desmoplakin bind to?

A

intermediate proteins, such as vimentin, design, and keratin

83
Q

what do tight junctions enforce?

A

force transport through the cell rather than around

84
Q

where do tight junctions form?

A

at the apical end of the lateral surfaces of each cell

85
Q

scaffolding proteins at tight junctions recruit proteins such as _________ to the junctions

A

F-actin

86
Q

how do tight junctions block lateral movement of lipids and proteins in the plasma membrane?

A
  1. lipids is blocked only in the outer monolayer/leaflet
  2. integral membrane proteins are completely blocked since they cross both leaflets
87
Q

what do the large extracellular loops of claudin do in tight junctions ?

A

form ion-selective pores to allow passage of specific ions

88
Q

def: region where the plasma membrane of cells are aligned and brought into contact, with a very small gap between (3nm)

A

gap junction

89
Q

at a gap junction, the plasma membranes of adjacent cells are joined by 2 hollow cylinders, called ___________, which are highly linked to each other by noncovalent interactions

A

connexons

90
Q

__________ are assemblies of 6 integral membrane subunits of _____________ proteins which form a circle

A

connexon, connexin

91
Q

T or F: connexon channels are non-selective

A

true

92
Q

gap junctions are the site of what kind of communication?

A

GJIC (gap junction intracellular communication)

93
Q

what kind of signals can be related by gap junctions?

A
  1. passed directly between cells, integrating cells into functional unist
  2. regulated by gating the channels
94
Q

how are connexins selective within eachtoher?

A

they must be compatible to form a gap junction that works, if they are incompatible, they form incompatible connexons

MBB 231 (19 decks)

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