Cytoskeleton

Question 1

What is the cytoskeleton comprised of?

Answer 1

Microtubules, actin and intermediate filaments

Question 2

Where is the cytoskeleton found?

Answer 2

ALL eukaryotic cells

Question 3

Describe the cytoskeleton

Answer 3

dynamic, complex, intracellular network of tubules, filaments and fibres

Question 4

What is the function of the cytoskeleton

Answer 4

give cells shape and function

Question 5

Where do microtubules start?

Answer 5

single point - microtubule organising centre

Question 6

What are the roles of microtubules

Answer 6

organisation of cell shape, movement and division

Question 7

Describe microtubules

Answer 7

hollow tubes of different lengths and sizes

Question 8

How do microtubules always exist

Answer 8

Dimers together

Question 9

What is a microtubule (structure)

Answer 9

hetero-polymer of alpha and beta tubulin with a GTP bound molecule

Question 10

How do the dimers in microtubules arrange themselves

Answer 10

end to end in protofilaments, forming a tube like structure of individual microtubules

Question 11

TRUE or FALSE - microtubules lack polarity

Answer 11

FALSE

Question 12

Which end of the microtubule grows slows

Answer 12

minus end

Question 13

Describe growth at the plus end of the microtubule

Answer 13

fast

Question 14

What can affect microtubule function

Answer 14

post-translational modifications and microtubule associated proteins

Question 15

What do microtubules form

Answer 15

mitotic spindle

Question 16

What acts to create dynamic instability in microtubules?

Answer 16

assembly and the minus and plus ends

Question 17

What makes up microtubules

Answer 17

tubulin heterodimers

Question 18

What does the minus end of tubulin become during assembly

Answer 18

mostly GDP

Question 19

What does the plus end of tubulin become during assembly

Answer 19

mostly GTP

Question 20

What does tubulin hydrolyse

Answer 20

GTP into GDP

Question 21

Where does hydrolysis of GTP occur fastest in tubules

Answer 21

Minus end

Question 22

What is the function of the plus end in microtubules

Answer 22

acts as a cap to protect growing microtubule

Question 23

What does the assembly of microtubules create

Answer 23

dynamic instabilty

Question 24

What end of microtubules promotes depolymerisation

Answer 24

plus end

Question 25

When does microtubule growth stop

Answer 25

when local concentration of GTP tubulin runs out

Question 26

What is the most stable part of the microtubule

Answer 26

base

Question 27

What is the microtubule organising centre important for?

Answer 27

polarity and maintaining permanent microtubule network in cell

Question 28

What is the microtubule organising centre comprised of?

Answer 28

pair of centrioles

Question 29

What is the function of gamma tubulin in the microtubule organising centre

Answer 29

forms special structure around end of individual microtubules, protects minus end from depolarisation

Question 30

TRUE or FALSE - ALL microtubules have the same polarity

Answer 30

TRUE

Question 31

Which end of the microtubule goes out into the cell

Answer 31

plus end

Question 32

What is a type of microtubule

Answer 32

basal body

Question 33

What do basal bodies give rise to

Answer 33

spindle poles

Question 34

What are microtubule associated proteins

Answer 34

proteins that interact with microtubules

Question 35

What is the function of microtubule associated proteins

Answer 35

regulate turnover of microtubules and promote assembly, stabilise microtubules and maintain function

Question 36

where is the function of microtubule associated proteins most important

Answer 36

nerve cells

Question 37

What are the motor proteins (microtubule associated proteins)

Answer 37

dynein and kinesin

Question 38

Describe Actin microfilaments

Answer 38

fibres of homomeric actin, highly conserved, cell type specific

Question 39

What is the structure of actin microfilaments

Answer 39

helical geometry, bound ATP

Question 40

What is the function of bound ATP in actin microfilaments

Answer 40

polymerisation

Question 41

What are the two forms of actin microfilaments

Answer 41

globular and filamentous

Question 42

How does actin exist in low concentrations

Answer 42

monomer

Question 43

What happens at the fast growing end of actin

Answer 43

new ATP actin is added

Question 44

What modulates actin filament turnover

Answer 44

nucleation factors and actin binding proteins

Question 45

What is the function of intermediate filaments

Answer 45

provide strength and structural support

Question 46

Where are intermediate filaments present

Answer 46

most eukaryotic cells EXCEPT fungi

Question 47

Which type of filament/tubule is the most complex

Answer 47

intermediate filaments

Question 48

Describe the structure of intermediate filaments

Answer 48

homo or heteropolymeric

Question 49

where are intermediate filaments found in the cell

Answer 49

cytoplasm

Question 50

Where can special forms of intermediate filaments be found

Answer 50

nucleus E.G. lamina

Question 51

What is the function of intermediate filaments in the nucleus

Answer 51

provide structural integrity

Question 52

What are the five subtypes of intermediate filaments

Answer 52

epithelial keratins, vimentin & desmin, neurofilaments, nuclear lamins

Question 53

Where do vimentin and desmin exist respectively

Answer 53

vimentin - fibroblasts | desmin - muscle

Question 54

What regulates the spontaneous self assembly of intermediates filaments

Answer 54

phosphorylation

Question 55

TRUE or FALSE - intermediate filaments lack polarity

Answer 55

TRUE

Question 56

Why do intermediate filaments lack polarity

Answer 56

due to anti-parallel strands