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lecture 7 Flashcards

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Biology 101 flashcards
1
Q

what is cell movement & changes and cell shape a combo of

A

cell proliferation, cell movement, tissue shaping

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2
Q

what are cell proliferation, cell movement, tissue shaping driven by

A

changes to cytoskeleton –> actin, microtubules, intermediate filaments

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3
Q

why is cytoskeleton useful for developmental processes

A

can be remodeled

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4
Q

what does rapid remodeling of cytoskeleton under plasma membrane lead to

A

changes of shape & dynamics; appendages being extended/retracted, adhering to surface, applying force to move it

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5
Q

property of every cytoskeletal filament system

A

ability to completely remodel depending on what cell wants it to do

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6
Q

describe cytoskeleton

A

hella dynamic; very easily remodeled, can be directed to fall apart or polymerize

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7
Q

what is cell remodeling a result of

A

intracellular signaling telling cells to move or divide

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8
Q

what controls dynamic ability of cytoskeleton

A

signaling pathways input onto cytoskeletal proteins

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9
Q

why is there cytoskelteon

A

control cell shape, tracks for vesicular traffic, generate force, structural strength

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10
Q

what is cell shape direct reflection of

A

internal cytoskeletal structure in cell

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11
Q

describe tracks for vesicular traffic

A

cargo within cell needs to be moved from point A to point B or secreted; move thru vesicles move around cytoskeletal tracks

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12
Q

how does non-muscle generate force

A

stress fibers

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13
Q

what are stress fibers

A

filaments of actomyosin that generate contractile force

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14
Q

what helps actin generate force

A

actin motor protein myosin 2 (non muscle myosin)

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15
Q

what would happen w/o cytoskeleton in terms of structure

A

there would just be plasma membrane, cell would be delicate as a bubble (no structural strength)

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16
Q

what does cytoskeleton do for cells etc.

A

gives structural strength

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17
Q

what happens when cell makes contact w/ surface

A

acto-cytoskeleton & other cytoskeleton are reorganized in response to signaling (initiated from this contact)

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18
Q

what happens due to cytoskeletal systems being reorganized

A

cells attach (grab onto cell surface, pull & stretch themselves), flatten, polarize, start moving

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19
Q

what happens to cell after it attaches n shit

A

dramatic changes in cell shape

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20
Q

what happens when cell polarizes

A

can tell front from back

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21
Q

what else do cells use cytoskeleton for

A

to generate cellular force

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22
Q

describe force produced by cytoskeleton

A

small, cuz cell is tiny af

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23
Q

how can we tell cell is producing force

A

cells attach & pull on pillars

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24
Q

what happens is nothing/no cells are pulling on pillars

A

no force is applied, cells stand straight up and down

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25
Q

what happens if cells are contacting pillars

A

attaches to pillar thru integrin interactions, pulls on pillar towards cell

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26
Q

basically what is cell tryna do while attached to pillar

A

its trying to spread out, and this pulls on pillar

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27
Q

what is myosin 2

A

motor protein that generates contractile forces

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28
Q

what happens if you added chemical inhibitor to myosin 2

A

pillar would go back straight (no contractile force)

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29
Q

what is vimentin

A

intermediate filament protein

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30
Q

what happens if mutation in vimentin

A

intermediate filament network is much weaker, skin is less strongly held together

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31
Q

what happens if you apply force in normal intermediate filament netowrk

A

no problem, no injury

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32
Q

what happens if you apply force to mutated intermediate filament

A

structural strength is compromised, shear off layers of dermis, form blisters (detachment of layers of tissue)

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33
Q

why are filamentous systems so dynamic & able to remodeled so quickly

A

bonds that hold these components together are H bonds (non-covalent)

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34
Q

what does non-covalent bonds mean in this context

A

weaker than covalent bonds –> easier to take apart, easier to form back together

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35
Q

why are systems so malleable, able to take diff shapes & forms, undergo rapid changes in shape & function

A

H bonds & electrostatic interactions

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36
Q

describe actin

A

individual actin proteins/monomers that come together & polymerize to form actin filaments

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37
Q

what are actin monomers

A

actin proteins

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38
Q

describe shape of actin polymer

A

helical polymer; natural twist

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39
Q

describe diff variety of actin filament shapes

A

filaments that are bundled together, branched actin network, etc.

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40
Q

why can actin be found in diff places in network

A

due to diff actin binding proteins helping shape network

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41
Q

where are actin filaments in cell

A

throughout cell, but most highly [ ] in cortex

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42
Q

describe actin in microvilli

A

give structure and function to microvilli (luminal surface of epithelial cells lining intestines)

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43
Q

what is integrin

A

receptors for extracellular matrix that helps cell grab onto things

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44
Q

describe actin/integrin

A

integrin cluster at end of long bundle of actin

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45
Q

what do actomyosin filaments do to actin

A

filaments generate forces to pull on integrin cluster to transmit force fron network to extracellular environment

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46
Q

where are integrin clusters

A

where cell is attached to surface

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47
Q

how big is microtubules

A

largest of 3; –> formes hollow filament netowrk

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48
Q

what is microtubule monomer

A

tubulin

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49
Q

what do microtubules form

A

trafficking network; vesicles travel along filament to find plasma membrane where they exocytose

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50
Q

basically what do microtubules do

A

provide tracks for vesicles to move along

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51
Q

what is another function of microtubules

A

in cilia; also helps segregate chromosomes

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52
Q

what are intermediate filaments

A

in b/w microtubules & actin in terms of size

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53
Q

describe intermediate filaments

A

woven together appearance –> hella stretchiness

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54
Q

what does this woven/stretchiness mean

A

can withstand hella force w/o breaking (will bend & stretch, not break)

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55
Q

what are intermediate filaments important for

A

structural strength

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56
Q

examples of intermediate filament proteins

A

vimentin, keratin

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57
Q

what are lamins

A

class of intermediate filaments found in nucleus, gives nucleus structural strength

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58
Q

what do these filaments work together to do

A

more complex cellular functions like migration & cell division

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59
Q

describe chemistry of individual microtubules & actin filaments

A

polarized; ends are chemically diff. from each other –> plus end & minus end

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60
Q

what does microtubules’ polarity result in

A

apical-basal polarity in epithelial layer

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61
Q

where do minus ends go

A

toward apical surface

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62
Q

where does plus ends go

A

basolateral surface

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63
Q

what does way to segregate diff components of cell (plus/minus end) give rise to

A

diff functional structures within cell

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64
Q

what drives overall cell polarity

A

microtubules

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65
Q

what is actin polarization more important for

A

how forces are generated inside cell

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66
Q

are intermediate filaments polarized

A

no

67
Q

describe stability of single protofilament/microtubules

A

thermally unstable; easy to remodel

68
Q

describe stability of multiple protofilaments

A

thermally stable

69
Q

why do we know what actin does from scientific POV

A

b/c when nature tries to kill us, does so by targeting actin cytoskeleton (stops respiration thru affecting contraction in diaphragm)

70
Q

what 3 chemicals/metabolites inhibit actin function

A

latrunculin, cytochalasin B, phalloidin

71
Q

what do latrunculin and cytochalasin B do

A

bind onto existing filaments and cause them to fall apart

72
Q

why does causing actin filament to fall apart stop its function

A

actin is no longer gonna function if its not in filament form

73
Q

what does phalloidin do

A

stabilizes actin to PREVENT it from falling apart

74
Q

why is phalloidin bad

A

prevents actin filament from getting any larger; locks it in place

75
Q

why is stabilizing or depolymerizing actin equally bad

A

systems need to be dynamic to function; need to grow AND shrink

76
Q

are all three equally lethal

A

yea

77
Q

what does latrunculin do specifically

A

depolymerizes thru binding actin subunits

78
Q

what does cytochalasin B do specifically

A

depolymerizes; caps filament plus ends

79
Q

describe how actin monomers join filaments (in terms of polarity)

A

plus end joins to minus end, minus end joins to plus end

80
Q

will two monomers ever join plus end to plus end

A

never; it’s like magnets repelling

81
Q

why does actin filament have plus and minus end

A

b/c polarity is maintained as filament grows since they come together in same orientation

82
Q

describe polarity of monomers

A

intrinsic polarity, two diff ends

83
Q

how do actin monomers come together

A

thru noncovalent bonds

84
Q

what is buried inside monomer

A

nucleotide; ATP

85
Q

what happens when monomer joins filament

A

ATP hydrolyzed to ATP

86
Q

describe nucleotide on monomers

A

always bound, just goes from ATP to ADP

87
Q

do microtubules have nucleotide

A

GTP

88
Q

what is RDS of formation of actin filaments

A

nucleation

89
Q

what happens when two actin monomers come together to form a dimer

A

unstable

90
Q

what is needed for actin filament formation

A

three monomers come together (it favors having a 4th join)

91
Q

what part of polymerization takes longest

A

start; b/c you wait for 3 monomers to randomly come together by chance

92
Q

what is nucleation

A

formation of actin oligomers

93
Q

what is nucleus of actin filament

A

trimer (b/c it favors formation of tetramer)

94
Q

describe lag phase

A

correpsonds w/ nucleation

95
Q

what happens initially

A

no growth; lag phase, waiting for 3 monomers to come tog.

96
Q

why is nucleation lag phase

A

you need 3 monomers to come together before you get stable growth

97
Q

what happens in growth phase

A

filaments spontaneously elongate

98
Q

what happens when it reaches EQ

A

filaments don’t shrink but no longer grow

99
Q

What is changing in test tube over time that causes shift from growth to equilibrium?

A

enough monomers means polymerization; monomers drop below critical concentration means it switches from growth to treadmilling or shrinking

100
Q

what happens if you dump in new monomers in test tube in EQ phase

A

would re-initiate logarithmic growth until it reaches a new EQ phase, where [ ] of free monomers are depleted again

101
Q

what does steady state situation/ EQ mean

A

Concentration drops as monomers are increasingly incorporated into filaments, growth is no longer possible because at that concentration, a monomer is just as likely to bind as it is to leave

102
Q

what are ATP bound monomers likely to do

A

polymerize

103
Q

what are ADP bound monomers likely to do

A

fall apart

104
Q

what happens if you added monomers to upper part of test tube only

A

those filaments would start to grow but the ones at the bottom wouldn’t grow because the [ ] down there would be different

105
Q

what happens after fist seed filament forms

A

monomers come together allowing for rapid growth/elongation

106
Q

what happens as monomers increasingly incorporated into filaments

A

[ ] drops, growth is no longer possible b/c at that [ ] monomer is just as likely to bind as it is to leave (critical [ ])

107
Q

what happens when it starts to polymerize/filament forms/binds together

A

triggers hydrolysis from ATP to ADP

108
Q

what are actin dimers

A

unstable

109
Q

what is magical moment for actin

A

3 monomers together –> rapid growth

110
Q

what does length of time in polymerized form favor

A

ADP formation

111
Q

longer actin protein is in filament, more likely

A

to have switched to ADP

112
Q

when does actin filament grow until

A

until [ ] of monomers drops below critical conc.

113
Q

what does below critical [ ] mean

A

no longer thermodynamically favorable for polymerization rxn to occur

114
Q

what does critical [ ] mean

A

rate of monomer addition equals rate of monomer loss (equal # monomers coming on as leaving) –> steady state situation

115
Q

critical [ ] of actin in test tube

A

0.1 micromolar

116
Q

what does above 0.1 um mean

A

filaments grow

117
Q

what does at 0.1 mean

A

filaments stay same size (steady state)

118
Q

what does below 0.1 mean

A

filaments shrink, actin leaving is favored

119
Q

what is actin [ ] inside cell

A

100 um; should mean that inside cell should all be filaments

120
Q

why isn’t inside of a cell all filaments

A

other regulatory proteins prevent actin from polymerizing when signals aren’t being received to direct polymerization

121
Q

in a test tube what determines whether actin filaments polymerize, depolymerize, treadmill

A

actin monomer concentration

122
Q

slowest step of actin polymerization

A

nucleation phase (need 3 monomers to come together in space & time to get first stable oligomer)

123
Q

what happens after lag phase

A

filament starts growing rapidly

124
Q

what happens as concentration of available actin monomers falls

A

reaches critical concentration

125
Q

what is critical concentration

A

exact [ ] of actin monomers where you have equal rate of addition as loss

126
Q

are plus and minus ends of actin similar or different

A

chemically different; diff chem structure & strength of interactions

127
Q

describe speed of plus end vs. minus end

A

plus end can grow/shrink 4x faster that minus end

128
Q

does stuff happen quicker at plus end or minus end

A

plus end

129
Q

what does a given [ ] of monomers favor

A

favors growth

130
Q

does plus end grow and minus end shrink?

A

both grow, just plus end grows faster

131
Q

why does plus end grow faster

A

things can join plus end 4x faster than at minus end

132
Q

what happens above critical [ ] for plus & minus ends

A

above it they both grow, below they both shrink

133
Q

is critical conc. same or diff for plus & minus ends

A

same

134
Q

plus vs. minus end, growing /shrinking

A

when growing or shrinking plus end does it 4x faster than minus end

135
Q

what does plus end of monomer bind to

A

minus end

136
Q

what does minus end of monomer bind to

A

plus end

137
Q

is minus end faster or slower for gaining + losing

A

slower

138
Q

what happens when monomers are floating around

A

ATP bound

139
Q

what happens when monomers are joined to a filament

A

ATP is hydrolyzed to ADP

140
Q

monomers are being added quicker than what

A

than time is takes to hydrolyze ATP to ADP

141
Q

what does ones to right of filament mean

A

have been in filament for less time

142
Q

what does ones to left of filament mean

A

been part of filament for more time (b/c added faster at plus end)

143
Q

what does distance along filament reflect

A

reflects how long they’ve been in filament

144
Q

what does monomers who’ve been in filament longer mean

A

have enough time to hydrolyze ATP to ADP

145
Q

what happens to monomers being added quickly (newer ones)

A

need a little more time after being added to go from ATP to ADP

146
Q

what is ATP cap

A

fast growing end is gonna have an ATP cap; certain # of actin proteins at plus end that remains attached to ATP

147
Q

which end has ATP cap

A

plus end (fast growing filament)

148
Q

which end doesn’t have ATP cap

A

minus end

149
Q

why does one end have ATP cap and other doesn’t

A

not just b/c they’re chemically different, it’s a different form of actin on either end (ATP at plus, ADP at minus)

150
Q

what does faster addition at plus end mean

A

takes time to hydrolyze ATP to ADP, leads to ATP cap at plus end

151
Q

why do plus and minus end have different critical concentrations

A

ATP actin is more likely to polymerize (cuz its ATP), while ADP actin more likely to leave

152
Q

what is at plus end (what kind of actin)

A

ATP actin

153
Q

what is at minus end

A

ADP actin

154
Q

which critical conc. is smaller

A

critical conc. of ATP smaller than ADP actin

155
Q

what is at minus end

A

addition isn’t favored, for a given [ ] of actin monomers it’ll stop being added at a higher conc. than plus end

156
Q

what is at plus end

A

addition is favored, need to have less actin monomers available before it stops being added

157
Q

what happens if you’re in between the range

A

particular conc. is less than critical conc. at minus end

158
Q

what happens if [ ] is in between conc. of ATP and ADP

A

plus end grows, minus end shrinks –> treadmilling

159
Q

what is treadmilling

A

in b/w critical conc. of minus end and plus end; minus end shrinks at same rate that plus end grows –> overall stays same length

160
Q

which critical concentration is bigger

A

minus end

161
Q

what does actin form

A

polarized filament w/ distinct chem properties at each end

162
Q

what does nucleotide hydrolysis lead to

A

treadmilling

163
Q

what is slowest step of actin polymerization

A

oligomer formation

bio 211 (18 decks)

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