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Biomed 2 > Cell Bio - Cell adhesion and signalling > Flashcards

Cell Bio - Cell adhesion and signalling Flashcards

1
Q

difference between planktonic and sessile bacteria

A

planktonic - freely existing in bulk solution
sessile - attached to a surface or within a biofilm

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2
Q

what does the extracellular matrix (ECM) consist of

A

network of proteins and polysaccharide chains that are manufactured by cells, secreted and modified outside the cell by several different enzymes.

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3
Q

what are the functions of the ECM

A

mechanical - tensile and compressive strength and elasticity
protection - buffering against extracellular changes and water retention
organisation - control of cell behaviour by binding of growth factors and interactions with cell surfaces

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4
Q

what secretes the matrix macromolecules

A

fibroblasts

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5
Q

what forms bones and cartilage

A

bones - osteoblasts
cartilage - chondroblasts

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6
Q

what are the main macromolecular components of the ECM

A

glycosaminoglycans
fibrous protein
non-collagen glycoprotein

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7
Q

structure of glycosaminoglycans (GAG)

A

GAGs are unbranched polymers of repeated disaccharide derivatives, including amino sugars, sulfated acetylamino sugars and uronic acids

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8
Q

what are the properties of GAG’s

A

Acidic and negatively charged
Attract positive ions (eg Na+) which attracts water causing gel formation
Comprise 10% of ECM mass but 90% of volume
GAGs (especially hyaluronan) provide compressive strength
Metabolically cheap bulking agent

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9
Q

what is hyaluronan

A

GAG
107kDa
spun out of the cell membrane

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10
Q

function of hyaluronan

A

used to hold together open spaces in the ECM that would otherwise be filled up with cells

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11
Q

structure of a proteoglycan

A

serine-rich protein decorated with hundreds of O-linked acidic or sulfated GAG’s

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12
Q

what is aggrecan

A

common proteoglycan in the ECM
Its core protein is decorated with around 100 chondroitin and 30 keratan chains.

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13
Q

what does aggrecan bind to

A

hyaluronan via adaptor proteins

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14
Q

what is the function of the primary cell wall in plants

A

flexibility allowing expansion and remodelling

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15
Q

composition of the primary cell wall

A

cellulose
hemicellulose
pectin

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16
Q

function of the secondary cell wall

A

rigid providing strength

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17
Q

composition of secondary cell wall

A

cellulose
hemicellulose
lignin

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18
Q

what accounts for 20% of primary cell wall dry weight

A

xyloglucan

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19
Q

what is the backbone of xyloglucan composed of

A

1,4-linked β-D-Glcp residues

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20
Q

what occurs to 1,4-linked β-D-Glcp residues

A

are substituted at O6 with mono-, di-, or triglycosyl side chains.

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21
Q

where does galacturonic acid occur (Gala)

A

homogalacturonan (HG)
rhamnogalacturonan (RG)

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22
Q

function of pectin demethylase

A

demethylates pectin
makes it available for crosslinking via Ca2+ bridges

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23
Q

what is an occluding junction

A

seals cells together forming an impermeable barrier

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24
Q

anchoring junctions

A

attaches cells to other cells or the ECM

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25
communicating junctions
allows exchange of chemical/electrical information between cells
26
function of adheren junctions
important role in determining shape of multicellular structures forms an indirect link between actin cytoskeletons
27
what do adhesion belts allow
reshaping of epithelial cells form vesicles
28
function of desmosome junctions
indirectly link intermediate cytoskeletons provides mechanical strength
29
what are channel-forming junctions
creates a link between the cytoplasm of two cells
30
what are plasmadesmata
plant equivalent to gap-junctions
31
structure of gap junctions
each channel is comprised of individual connexin subunits can be homomeric or heteromeric assemble into homotypic or heterotypic channels
32
where are new connexons added
periphery via exocytosis
33
what does a mutation in connexin 26 lead to
– mutation leads to death of cells in the organ of Corti (electrically active sensory epithelium) Congential deafness
34
what can mutations in connexins lead to
cateracts and demyelinating disease in peripheral nerves
35
what is a signal-relaying junction
basically a synapse
36
difference between cadherins and integrins
cadherins - mediate cell-cell attachment integrins - mediate cell-matrix attachments
37
what proteins constitute tight junctions (TJ)
claudin junctional adhesion molecules (JAM's) occludin ZO
38
what is claudin
a four-pass transmembrane protein that constitutes TJ strands
39
what are junctional adhesion molecules (JAM's)
class of cell–cell adhesion molecules with two Ig repeats that localize to TJs.
40
what are occludins
four-pass transmembrane protein localized at TJs.
41
what are ZO proteins
(zonula-occluding) family proteins: TJ- undercoating scaffolding proteins
42
where are cadherins found and not found
in all animals and choanoflagellates not present in plants, fungi, archaea or bacteria
43
name a non-classical cadherin and its function
desmocollin forms desmosome structures
44
why is Ca2+ important for cadherin function
binds to the hinge regions of cadherin, prevents flexing removal of Ca2+ reduces binding affinity at N-terminal destabilisation leads to proteolytic degradation
45
function of catenins
form a link between the intracellular cadherin domain and the actin filament
46
what is the dual role of β-catenin
Intracellular anchor protein at adherens junctions Transcriptional regulator in Wnt signalling
47
function of vascular endothelial cadherin (VEC)
required for endothelial survival required for response to vascular endothelial growth factor (VEGF) VEGF binds to a receptor tyrosine kinase that requires VE cadherin as a cofactor
48
structure of integrins
Comprised of 2 non-covalently associated glycoprotein subunits Short intracellular C-terminal - Large extracellular N-terminal domain
49
difference in roles of the extracellular domain and the intracellular domain of integrin
extracellular - binds extracellular matrix proteins or cell surface ligands of other cells intracellular - links (usually via Talin) to the actin cytoskeleton
50
what does allosteric regulation allow for
switching between active and inactive state
51
describe outside-in activation of integrins
Binding of an extracellular ligand to an integrin results in binding to the cytoskeleton Transmission of a force via the cytoskeleton
52
describe inside-out activation of integrins
Intracellular regulatory molecules such as phosphoinositide (PIP2) activate Talin Causes strong binding of Talin to β integrin chain In turn this activates the extracellular domain of integrin to bind extracellular ligands PIP2 can be produced in response to extracellular signals. Complex crosstalk between different signalling processes
53
what is heterophilic binding
binding to a different type of molecule
54
what is a lectin and their function and an example
cell surface carbohydrate binding protein Mediate transient cell-cell adhesion in the bloodstream Control binding of white blood cells to the endothelial cells lining the blood vessels
55
what are the 3 different types of selectins and where are they present
L-selectin - on white blood cells P-selectin - on platelets and endothelial cells activated by an inflammatory response E-selectin - on activated endothelial cells
56
what causes lymphocytes to bind and become trapped
In lymph organs endothelial cells express oligosaccharides recognised by L-selectin on lymphocytes
57
structure of intracellular adhesion molecules (ICAM)
ICAMs have an extracellular domain characteristic of antibodies
58
difference between ICAM/VCAM and NCAM in terms of binding
ICAM/VCAM - heterophilic binding to integrins NCAM - homophilic binding
59
what charge do neural cell adhesion molecules (NCAM) have and why
negative high concentration of sialic acid chains
60
what are the difference between cadherin and NCAM mutations
cadherins - lethal NCAM - more subtle effects
61
how does fascicilin3 function
functions in recognition of the tissue by neuronal growth cones
62
what does fascicilin3 form
homophilic adhesions
63
what holds the pre/post-synaptic membranes together
cadherins Ig superfamily neuroligins neurexins
64
where does plant cell adhesion occur
middle lamella - pectin rich domain
65
what are the different domains of pectin
HGA - homogalacturonan RGII - rhamnogalacturonan I RGI - rhamnogalacturonan I XGA - xylogalacturonan
66
what can cause loss of plant cell adhesion
Defects in synthesis of plant cell wall polysaccharides
67
what are the advantages of single cell organisms for models
Fast growth in chemically defined media Relatively cheap culture media Several molecular tools for manipulation Extensive knowledge of its genetics and genomics Extensive knowledge on its transcriptome, proteome, and metabolome Several strains are considered biosafety level 1 (K12)
68
what are the disadvantages of using single celled organisms for models
doesn’t have a nucleus/chromatin, not all protein modification mechanisms e.g. glycosylation
69
features of yeast as model organisms
Rapid growth (1.5 or 2.5 hours) Non-pathogenic Efficient transformation by exogenous DNA Efficient homologous recombination Simple genetic screens
70
what are the advantages of organoids over 2D cultures
more physiologically relevant than monolayer culture models. far more amenable to manipulation of niche components, signalling pathways and genome editing compared to in vivo models.

Biomed 2 (18 decks)

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