The Cytoskeleton

Question 1

the cytoskeleton provides strength and shape, playing a central role in movement and division by driving and guiding intracellular ???

Answer 1

organelle traffic

Question 2

Microtobulues are hollow or solid tubes?

Answer 2

hollow

Question 3

microtubules are formed from ??? dimers and are 25nm big

Answer 3

tubulin

Question 4

microfilaments are a double helix made of ??? monomers and are about 7nm big

Answer 4

actin

Question 5

intermediated filaments are a strong fibre composed of ??? subunits and are 8-12nm big

Answer 5

protein

Question 6

what is an example of the cytoskeleton’s ability to rapidly reorganise?

Answer 6

a fibroblast

Question 7

TRUE or FALSE: the cytoskeleton is responsible for large-scale cellular polarity which allows cells to tell the difference between top, bottom or front and back

Answer 7

TRUE

Question 8

what is the largest structural element of the cytoskeleton?

Answer 8

microtubules

Question 9

microtubules are rigid and typically have one end attached to a ???

Answer 9

microtubule-organising centre

Question 10

cytoplasmic microtubules pervade the cytosol and are responsible for maintaining/altering cell shape, placement and movement of vesicles, formation of mitotic and meiotic spindles and ???

Answer 10

maintaining axons

Question 11

are axonemal or cytoplasmic microtubules responsible for placement and movement of vesicles?

Answer 11

cytoplasmic MTs

Question 12

what part of the cytoskeleton is responsible for the formation of mitotic and meiotic spindles?

Answer 12

cytoplasmic Microtubules

Question 13

axonemal or cytoplasmic Microtubules include he organised and stable microtubules in structures such as cilia/flagella and the basal bodies to which they attach

Answer 13

axonemal

Question 14

the basic subunit of a microtubule protofilament is a heterodimer of ???

Answer 14

tubulin

Question 15

microtubules are composed of one alpha tubulin and one beta-tubulin bound COVALENTLY or NON-COVALENTLY to each other?

Answer 15

non-covalently

Question 16

are all the dimers of microtubules or intermediate filaments oriented the same way?

Answer 16

microtubules

Question 17

how do microtubule protofilaments have an inherent polarity?

Answer 17

because of dimer orientation

Question 18

microtubules are hollow cylindrical structures built from 13 parallel ??? of tubulin protein

Answer 18

protofilaments

Question 19

microtubules will self-assemble in-vitro but ??? is the rate limiting step

Answer 19

nucleation

Question 20

nucleation of microtubules creates a ring structured microtubule seed for growth but this is slow. More commonly seeded by ??? ring in microtubule organising centre to be speedier

Answer 20

gamma-tubulin ring

Question 21

microtubules originate from ??? within the cell. Centrosomes near the nucleus and basal bodies near the cell membrane in cilia/flagella

Answer 21

microtubule-organising centres

Question 22

microtubules grow outwards from microtubule-organising centres with a fixed polarity where the MINUS or PLUS (?) ends are anchored in the MTOC

Answer 22

minus ends

Question 23

dynamic growth and shrinkage of microtubules occurs at the PLUS or MINUS end?

Answer 23

plus

Question 24

MTs form by the reversible polymerisation of dimers in the presence of ??? and Mg2+

Answer 24

GTP

Question 25

what is a unique property of microtubules?

Answer 25

their ability to constantly polymerise and depolymerise i.e. dynamic instability

Question 26

microtubule binding proteins modulate filament dynamics and ??? and can also mediate the interaction of microtubules with other cell components. i.e. tau proteins

Answer 26

organisation

Question 27

microtubule targeting agents interfere with ??? and alter equilibrium between subunits

Answer 27

tubulin assembly/disassembly

Question 28

TRUE or FALSE: Disruption of microtubules induces various cellular responses often leading to cell cycle arrest or cell death

Answer 28

True

Question 29

an example of a microtubule targeting agent is ??? which comes from a yew tree and binds along filaments to stabilise them

Answer 29

taxol (paclitaxel)

Question 30

an example of a microtubule targeting agent is ??? which comes from an autumn crocus and caps both filament ends to depolymerise the microtubule

Answer 30

colchicine

Question 31

microtubules allow for nutrient transport in neurons. Tau helps support these microtubules, but hyperphosphorylated Tau forms affrefates, dissociating from MTs and staving the neurons = ???

Answer 31

alzheimers

Question 32

Microfilaments are helical polyemers of actin that are flexible and are dispersed throughout the cell but most concentrated in the ??? beneath the plasma membrane

Answer 32

cortex

Question 33

microfilaments develop and maintain ??? and are involved in cell migration and cytoplasmic streaming.

Answer 33

cell shape

Question 34

what is the structural core of microvilli?

Answer 34

microfilaments

Question 35

microfilaments are composed of actin subunits that are a 375-amino-acid polypeptide carrying a tightly associated molecule of ??? or ???

Answer 35

ATP or ADP

Question 36

microfilament actin subunits assemble head to tail to form a ???

Answer 36

protofilament

Question 37

two microfilament protofilaments form a helix held together by ??? contacts

Answer 37

lateral

Question 38

like tubulin, the actin protofilaments composing ??? have polarity and the ends differ chemically and structurally

Answer 38

microfilaments

Question 39

Globular‐actin (G-actin) monomers REVERSIBLY or IRREVERSIBLY (?) polymerise into actin microfilaments (“F‐actin”). G‐actin is added rapidly at the plus end and slower/lost at the minus end. G‐actin monomers nucleate slowly but then can assemble onto MF more rapidly, bound ATP is then slowly hydrolysed to ADP. Growing MF ends have ATP‐actin, whereas most of the MF is composed of ADP‐actin

Answer 39

reversibly

Question 40

G-actin is added rapidly at the PLUS or MINUS end of a microfilament and slower at the opposite end

Answer 40

plus

Question 41

subunits of ??? cycle rapidly between free and filamentous states and have the ability to maintain a constant length despite a net flux of subunits through the polymer

Answer 41

microfilaments

Question 42

treadmilling of microfilaments occurs at a subunit concentration where filament growth balances ??? Requires ATP hydrolysis for energy

Answer 42

shrinkage

Question 43

what type of energy does treadmilling of actin filaments require?

Answer 43

ATP Hydrolysis

Question 44

actin binding proteins influence filament dynamics and organisation. E.g. ??? stimulates filament elongation

Answer 44

profilin

Question 45

TRUE or FALSE: the role of microfilaments can be determined through chemical inhibition that can be used to unsettle microfilaments

Answer 45

TRUE

Question 46

lactrunculin is a drug that ??? by binding to actin subunits. Originally found from sponges

Answer 46

depolymerises

Question 47

cytochalasin B depolymerises actin by capping the filaments ??? ends. comes from fungi

Answer 47

plus

Question 48

phalloidin stabilises acting by binding along filaments. Comes from the ???

Answer 48

amanita mushroom

Question 49

Mutations in the skeletal muscle α‐actin gene (ACTA1) may affect its ??? binding ability and cause a range of congenital myopathies. People with actin-accumulation myopathy have severe muscle weakness (myopathy) and poor muscle tone (hypotonia) throughout the body e.g. Floppy baby syndrome

Answer 49

ATP

Question 50

intermediate filaments are the most stable component of the cytoskeleton, conferring strength on tissues. they are rope-like fibers with a ??? diameter

Answer 50

10nm

Question 51

intermediate filaments are assembled from basic structural units consisting of two intermediate filament ??? intertwined into a coiled-coil

Answer 51

polypeptides

Question 52

the two dimers of intermediate filaments are ???

Answer 52

aligned in parallel

Question 53

parallel dimers align laterally to form a tetrameric protofilemt which overlap to build a filamentous structure ~8 protofilaments thick. Intermediate filaments or microfilaments?

Answer 53

intermediate filaments

Question 54

types of intermediate filaments can be: - nuclear (lamins) - Vimentin-like (vimentin, desmin) - epithelial (???) - axonal (neurofilament proteins)

Answer 54

keratin

Question 55

A single epithelial cell can produce multiple types of keratins which co‐polymerise into a single network held together by ??? bonds

Answer 55

disulfide

Question 56

??? impart mechanical strength by anchoring the intermediate filaments at sites of cell–cell and cell matrix contact – desmosomes and hemidesmosomes

Answer 56

keratins

Question 57

epidermolysis bullosa simplex: Occurs when defective keratins are expressed in the ??? of the epidermis. Results in the skin blistering to even mild mechanical stress

Answer 57

basal cell layer