cytoskeleton

Question 1

definition of cytoskeleton

Answer 1

cytoskeleton consist of filamentous bio-polymers (microtubules, F-actin and intermediate filaments) and oaf associated proteins that modulate the activity, dynamics and organisation of the cytoskeleton (actin binding or microtubule binding proteins, such as molecular motors)

Question 2

filamentous bio-polymers in the cytoskeleton

Answer 2

microtubules, F-actin, intermediate filaments)

Question 3

proteins associated with the cytoskeleton

Answer 3

actin binding or microtubule binding proteins, such as molecular motors

Question 4

eukaryotic cytoskeleton provides

Answer 4

tracks that link the regions of the cell

Question 5

skeleton

Answer 5

–> connects all parts of the cell–> supports motility–> helps spatial organisation

Question 6

F actin location

Answer 6

found closest to the membrane

Question 7

microtubules location

Answer 7

spans from the centrosome to the outside of the cell

Question 8

intermediate filaments

Answer 8

found all around the cell

Question 9

three classes of filaments that make up the cytoskeleton

Answer 9

f actin, microtubules, intermediate filaments

Question 10

f actin also known as

Answer 10

microfilaments

Question 11

F actin

Answer 11

7-9nm –> short range transport and cell migration

Question 12

Microtubule

Answer 12

25nm –> long range transport and chromosome inheritance (mites, meioses)

Question 13

<p>intermediate filaments</p>

Answer 13

mechanical strength

Question 14

cytoskeleton as well as proving tracks for intracellular trafficking, also provides..

Answer 14

stability for the cell e.g. extreme example: membrane cytoskeleton of red blood cells make them stiff and strong

Question 15

structure of F actin

Answer 15

• made up of G actin monomers-f actin is made up of 2 photo filaments-actin exists as monomers and polymers-F actin will release G actin- cell switches between g and f actin

Question 16

most actin in the cell is

Answer 16

G actin

Question 17

how many different actin binding proteins ar known

Answer 17

160

Question 18

what do actin binding proteins d

Answer 18

they modify actin organisation

Question 19

actin forms

Answer 19

cellular protrusion e.g. sterocilia on hair cells in the inner eare.g. microvilli on an intestine epithelium

Question 20

examples of different formations of actin

Answer 20

stabilising, capping, depolymerising, cross-linking, severing, moving, bundling

Question 21

ordered bundling

Answer 21

microvilli, sterocilia

Question 22

dynamic crosslinking

Answer 22

stress-fibres and muscle

Question 23

cross linking

Answer 23

network formation

Question 24

myosin is used in

Answer 24

actin in a ‘moving’ formation

Question 25

firkin, alpha-actinic is used in

Answer 25

bundling and stabilising

Question 26

filamin, spectrum are used in

Answer 26

sequestering/recycling and branching

Question 27

G actin is polymerised by

Answer 27

'treadmilling'

Question 28

what is treadmilling

Answer 28

adding subunits at one end, losing them at the other

Question 29

without actin binding proteins

Answer 29

the cell would die e..g all the G actin would polymerise

Question 30

the bundles actin forms make it

Answer 30

a strong molecule

Question 31

single actin chains are

Answer 31

flimsy and week

Question 32

cilia are just

Answer 32

huge bundles of actin

Question 33

microtubules are made up of

Answer 33

beta and alpha tubular (tubulin dimer) and these polymerise into protofilliment (straight line) which joins to form a microtubule

Question 34

13 protofilaments

Answer 34

form a microtubule

Question 35

at one end of the microtubule there will be

Answer 35

Beta tubulin

Question 36

at the other end of the microtubule will be

Answer 36

an alpha tubule

Question 37

microtubule size

Answer 37

25nanometer diameter

Question 38

without GFP what cannot be visualised

Answer 38

microtubules --> gives out light and make it look larger than it really is

Question 39

tubular exists as..

Answer 39

dimers and polymers

Question 40

tubular is fairly dynamic and this is due to

Answer 40

polymerisation behaviour

Question 41

tubular is added and released at

Answer 41

one end of the polymer

Question 42

polymerisation of tubulin- polymerisation

Answer 42

1)polymerisation- GTP-bound tubular dimers get added to 'plus end'. A cap of GTP tubular stabilises the growing microtubule

Question 43

polymerisation of tubulin- pausing

Answer 43

water is added to GTP tubular to form GDP tubular and phosphate. when polymerisation slows down (e..g not enough tubular available), the GTP cap disappears

Question 44

polymerisation of tubulin- depolymerisation

Answer 44

-microtubule becomes unstable and depolymerises and this moment of transition is called a CATASTROPHE

Question 45

polymerisation of tubulin- second polymerisation

Answer 45

GTP tubular can bind to the shrinking microtubule and establish a new cap. The meant of transition is called a RESCUE EVENT

Question 46

microtubules constantly switch from

Answer 46

growing and shrinking

Question 47

growing and shrinking

Answer 47

dynamic instability

Question 48

recue event

Answer 48

moment of transition when GTP tublin begins to bind again

Question 49

GTP cap needs to be present for the

Answer 49

microtubule to grow

Question 50

what reveals the difference in dynamic behaviour of microtubules and F-actin

Answer 50

speckle microscopy

Question 51

which part of the microtubule is dynamic

Answer 51

the ends of the microtubule--> while incorporated tubular remains relatively stationary--> only change in colour at the ends of the microtubule

Question 52

which parts of F-actin are dynamic

Answer 52

actin treadmills through the actin filament meshwork--> can see flow of action--> due to tread milling of fluorescent subunit throughout the actin filament

Question 53

intermediate filaments

Answer 53

relatively unorganised and made of many different types of proteins. provide strength to organisms, since animal cells do not have a cell wall and the plasma membrane is liquid

Question 54

which types of proteins are present in intermediate filaments

Answer 54

keratin, lamina, pimentos (ends are globular)

Question 55

formation of intermediate filament

Answer 55

a coiled coil consisting of alpha-helices. made up of 2-3 helices, which wind around each other

Question 56

alpha helices in intermediate filaments are often..

Answer 56

amphipathic

Question 57

amphiphatic

Answer 57

charged at one site --> serves protein interaction

Question 58

often intermediate filaments have a structural similarity but are

Answer 58

made up of different proteins e.g. keratin or vimentin

Question 59

formation of intermediate filaments does not require

Answer 59

ATP or GTP --> self assemble into apolar filaments (not polar or dynamic)

Question 60

nuclear lamina are made out of

Answer 60

intermediate filaments

Question 61

lamins provide stability and organise the

Answer 61

nucleus

Question 62

phosphorylation leads to

Answer 62

fragmentation of lamins

Question 63

what allows cell movement

Answer 63

the intermediate filaments can be reorganised by disassembling into subunits

Question 64

which skin associated structure are formed by intermediate filaments

Answer 64

nails, hair , eye (lens)