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Cell biology > week 8 > Flashcards

week 8 Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

where is the contractile ring

A

at the metaphase plate

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1
Q

examples of actin and myosin in non-skeletal muscle cells

A
  • cytokinesis, smooth muscle, vesicle transport, cytoplasmic streaming, cell migration
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2
Q

what does the organization of a contractile ring resemble

A
  • sarcomere, just rolled in
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3
Q

wehre to tind sarcomere-like structures

A
  • contractile ring (different because not stable, contraction requires the loss of components)
  • adhesion belts (contractile rings formed when you want to compress things)
  • ## stress fibers (migrating cells)
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4
Q

difference of actin an dmyosin in non-skeletal muscle cells

A
  • structures are not stable, whereas structure in sarcomere of our muscle is stable.
  • things here are constantly being polymerized and depolymerized
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5
Q

how is smooth muscle contraction regulated

A
  • myosin phosphorylation.
  • calcium activates a CaM kinase
  • kinase activates myosin light chain by phosphorylation, allows for conformational change and contaction
  • light chains form a filament resembling a thick filament
  • altering conformation of myosin and heavy chain
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6
Q

why can smooth muscle contraction be more persisntent

A
  • ## no T and t, myosin can hold on and bind to actin at same time
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7
Q

is smooth muscle contraction or skeletal muscle contraction faster

A
  • smooth muscle lacks trop and trop
  • smooth muscle is more persistent contraction than skeletal muscle
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7
Q

vesicle transport

A
  • formin is localized in the buds, and acts as a plus endnucelating site, actin polymerized at these sites.
    (rho gtp also there)
  • minus end is being pushed away when polyemrizing
  • end up with plus end in bud, xo myosin 5 can move in and transport everything
  • myosin 5 alwso pulls nucleus into bud by pulling on mictorubule cyctoksletion
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8
Q

how is myosin 5 actiavted

A

must be activated, only when bound to cargo, can transport many different type sof carho

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9
Q

what organism is used to observe vesicle transport

A
  • budding yeast cell/fisiion also
  • formation of a small bud that has a cell wall, must get material in the bud into the daughter cell
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10
Q

what is actin capped by in vesicle transport

A

formin

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11
Q

what does vesicle transport do

A
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12
Q

what special interaction takes place in vesicle transport

A
  • positioning of nuclear via Mts
  • interaction of actin and microtubules
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13
Q

cytoplasmic streaming functions

A
  • helps in diffusion/gas exchange in plant cells
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14
Q

cytoplasmic streaming process

A
  • cortical actin network track around plant cell transports things
  • as things are moved along actin cytoskeleton, causes movement in cytoplasm which makes gas exchange and diffusion more efficient
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15
Q

when is cell migration important

A

particularly in embryogenesis, and sometimes in adults

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16
Q

when does cell migration happen in adults

A
  • immune response
  • in injury, for repairs
  • pregnancy
  • cancer
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17
Q

focal adhesions

A
  • where cell sticks to substrate
  • located on either side of the stress fibres
  • actin cytoskeleton linked to transmembrane integral proteins that linkmto EC matrix (links cytoskeleton to eC matrix, so that when cell moves, cytoskeleton contracts
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18
Q

chemotaxis

A
  • there are receptors for the chemoattractant all around cell
  • ligand. binds to dreceptor
  • triggers cell movement
  • actin polymerization in that direction and membrane is pushed forward (involves fillapodia and lomellapodia)
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19
Q

actin in dominant active rho cell

A
  • rho always on which activates forming to make stress fibres
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20
Q

actin in control cell

A
  • fluorescent lining on exterio
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21
Q

actin in dominant active cdc 42

A
  • creates lots of fillapodia
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22
Q

actin in dominant active rac

A
  • ruffling caused by making lots of lamella podia randomly in cel all around
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23
Q

scratch closure assay

A
  • confluent (contact inhibited cells) are scratched, and filled in,
  • in inactive forms. of either of the three molecules (arc, cdc 42 or rho), there is no wound closure i.e. no cell migration
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24
Q

what is the order of activation of the three important players in cell mgiration

A

cdc42, rac, rho

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25
Q

cdc42 functions in cell migration

A
  • activates WASP, then ARP2/3 which causes actin poylermziation and formation of filopodia
  • also coordinates actin microtubules and polarity by activating par6
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26
Q

par6

A

tells us where the rfron of the cell is
- in response to par6, you will have poylermizing icotubles coin

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27
Q

what happens in response to cdc42 activation at the front

A
  • chemoattractant activates receptor, activates cdc42
  • wherever cc42 is active is the front
  • rac activation leading to arp2/3 acivation = more networking at front
  • rho activation leading to myosin 2 activation= polymerize actin budneles with forming and activate myosin so they become stress fibres
  • coordinates cell with other city networks (e.g. activates par6 molecule so that everything knows where front of cell is so everything can transport things there)
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28
Q

basic subunit of intermediate filaments

A

tetramer; the 2 dimers that come together in antiarallele fashion means there is no polarity because teh two sides are teh sme.

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29
Q

characteristics of intermediate cilmanets

A
  • not flobular
  • no nucleotide (atp or gtp) needed
  • no polaroty
  • no known motor proteins
  • less dynamic
  • involved in cella nd tissue integrity
  • assembled onto pre-existing elements
  • great tensile strength
  • actin and tubulin can be quickly polymerized anddepolymierzine,but not if
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30
Q

Main types of if

A
  • keratins
  • design, veimentin
  • neurofilaments
  • lamins
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31
Q

keratin

A
  • epithelial cells, tissue strength an inteigry
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32
Q

desmin

A

muscle cells, striated and smooth. provides ontegrity to muscles cells, supports smooth an strained.
- sarcomere organization, integrity

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33
Q

vimentin

A
  • mesenchymal cells (life (migratin cells0
  • e.g. rirboblast
  • provides integrity to migrant celsll
  • sarcoma organization, integrity
34
Q

neurofilametns

A

providee structure to axon
- found in neurons
- has that staggered non conitoujs structure
- axon organization

35
Q

lamina

A
  • found in nucleus
  • involved in nuclear structure and organization
  • support to ncuelcues
  • provide structure to nuclear memernsae
  • nucelar structure and organizzato
36
Q

plectin cross-links wjat

A

IF vimentin and micotbubles

37
Q

intermediate filament associated proteins like plectin

A
  • help link IF to other things in membrane (for e.g. other cyto components)
38
Q

in wha t form must Rac Rho and cdc42 be in for cell migration (these are th Rho proteins)

A
  • proteins must be in gtp form to be active and involved in actin polyermization
39
Q

stress fibres in cell migration

A
  • associated with cell adhesion are long actin fibres
  • interact with myosin and other regulator moecuels
  • are contraitle
  • bundles of actin
  • sarcomere-like organization
  • stress fibres contain focal ahdesions
40
Q

what are the types of cell adhesion

A
  • tight junctions, gap junctions, cell-cell adhesions, cell-eCM adhesions
41
Q

epithelial cells will be the focus, describe the characteristics

A
  • they form the barrier, skin, intestine lungs
  • help regulate what is transported across them
  • have polarity because they have an apical and basal surface
42
Q

apical surface of epithelial cells

A

outer surface, e..g gut lumen facing the food in our intestine

43
Q

basal surface

A
  • facing the EC matrix/connectiec tissue in the eC matrix, and basal lamina
44
Q

that makes up the EC matrix

A
  • the basal lamina, and the connective tissue
45
Q

basal lamina

A
  • a sheet of proteins
46
Q

how does adhesion in epithelial cells happen

A
  • desmosomes and IF
  • hemidesmosomes that link the cells to the EC matrix
47
Q

gap junctions

A
  • allow communicaiton and passage via small molecules
  • channel regulated by calcium
  • allow the passage of ions so epithelial cells usually haec the same concentration of ions which is important for transport across epithelial cells
48
Q

what are gap junctions composed of

A
  • 6 connexins from a connexon
  • each gap junction is essentially 2 connexons, so 12 connexins total
  • there are different types of connexin proteins classified by their molecular weight
49
Q

what happens when there is cell damage

A
  • this leads to high levels of calcium inside the cell cytoplasm
  • inner sides of connexins are not usually exposed to calcium
  • this causes the gap junctions to close
50
Q

tight junctions

A
  • membranes form adjacent cells form barrier
  • rows of occludin, claudin, and JAM proteins in each cell, apical surfaces of the membranes must be bound together by the three proteins
  • we want membranes of cells to be tightly bound to avoid formation of tight junctions
51
Q

are gap and tight junctions strong

A
  • not really, have important functions but not really involved in strength
52
Q

cell adhesion

A
  • homophobic interactions an heterophilic interactions
  • homophile
53
Q

homophilic interactions

A
  • cadherins
  • IG superfamily
    ** are on the same molecules, proteins present on once cell are present on antother cell to get the adhesion
54
Q

terophilic interactions

A
  • integrins
  • selectins
  • cell-cell or cell-eco
  • adhesion between diff molecules
  • one is bound to PM and the other is bound to EC matrix?
55
Q

Ig superfamily

A
  • mediates calcium independent homophilic cell adhesion
  • NCAM, ICAM
  • some homology to immunglobins not in function
  • homophilic
  • both cells need NCAM for ex
  • transmembrane
56
Q

cadherins

A
  • over 40 types
  • homophilic
  • single transmembrane domain
  • cytosolic C terminal tail that is associated with cytoskeleton
  • transmembrane
  • ## EC domain of the protein on one cell interacts with that of another cell
57
Q

are cadherin binding or ig superfamily calcium depencent

A
  • only chagrin is acA DEPENDENT
  • NEED CA TO BIND TO EACH OTHER
58
Q

types of cadhersns (remember that tu must have two of teh same in order for cells to bind together)

A
  • E cadherin (epidermal tissues)
  • N cadherin (nervous tissues)
59
Q

what happens when cadherins interact with the cytoskeleton inside the cell

A
  • they can create adherent junctions
  • when these line up with each other, can form a circumferential belt that can be contractile
60
Q

how do most cell adhesion structure slink to the cytoskeleton

A

-n in a way that that allows cell signalling
- cells now if they are linked to each other or not
- adhesions can signal to cell nucleus if things are broken
cytoplasc domain can link to the cytoskeleton

61
Q

what happens when cell adhesion is broken

A
  • signalling cascades
62
Q

what structures can form when cadherins link to actin cytoskeleton

A
  • can form contractile circumferential belt or adherens junctins
63
Q

what structures form when cadherins link to IF such as kertain

A
  • desmosomes
64
Q

adapter proteins

A

allow cadherins to link to teh cytoskeleton, for both actin and IF
- will signal to nucleus when cells pull apart for example, signal of adhesions e.g. beta catenin

65
Q

desmosomes

A

link the intermediate cytoskeleton with cahderins

66
Q

what cell surface do contractile rings act on

A

the apical surface e.g for contraction

67
Q

what are gap junctions good for in the cell

A
  • communicaiton
68
Q

ECM proteins examples

A
  • proteoglycans
  • collagens
    -laminin
    -fibronectin
69
Q

functions of eC matrix

A
  • anchoring and surrounding cells to mtainin cell archietecutre
  • control cell functions such as cell polarity, survival proliferation differentitaotn, fate etc
  • inhibit or facilitate cell mifraitn
  • bind to nd act as a reservoir of growth factors e.g. setting up concentration gradients of the factors, acting as co-receptor for the factors etc
  • activation of cell surface signalling receptors
70
Q

proteoglycans

A
  • hydrophilic, fourd in joints, hydration and residency (e..g lens in eye)
  • absorb water
71
Q

collagens

A
  • structural fuctions
72
Q

laminin

A

adhesion, migration

73
Q

fibronectin

A
  • migration, adhesino
74
Q

integrins

A

-heterodimeric transmembrane protein (alpha and beta subunit)
- heterophilic interactions with EC matrix componenta
- have different combinations of alpha and beta subunits
- bind to core RGD amino acids but require nearby synergy regions for specificity

75
Q

alpha1beta1

A

collagen

76
Q

alpha5beta1

A

fibrongctin

77
Q

alpha6beta1

A

laminin

78
Q

intern interaction with actin

A
  • stress fiber, forms focal adhesion at fibronectin resulting in stress fibre
79
Q

integrin interaction with iF like keratin

A
  • hemidesmosome formation, non migratory cells,
  • keratin with lamina integral protein
80
Q

inactive integrin

A
  • cannot bind tot he ligand (RGD sequence), cannot bin to EC matrix
81
Q

when would intern be activated

A

e.g. in cell migration when needing to form focal adhesion, integral protein would interact with RGD sequence of fribonectin??

82
Q

how can cell sense when the intern is bound to substrate

A
  • through signalling cascades
83
Q

selectins

A
  • homophobic adhesion molecule
  • binds oligo
  • involved in extravastion
84
Q
A

Cell biology (15 decks)

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