cytoskeleton

Question 1

what are 3 functions of the cytoskeleton in cells

Answer 1

division of chromosomes in mitosis- cytokinesis
drives organelle movemetn
support for plasma membrane

Question 2

describe 5 commonalities of actin, microtubules and intermediate filaments

Answer 2

made from repetitive subunits for flexibility
helical arrangement
held together by non covalent links
different properties due to different structures
interconnected system of bundled fibres and lattices

Question 3

where do actin, microtubules and intermediate filaments extend from

Answer 3

nucleus to plasma membrane

Question 4

what are microtubules

Answer 4

polarised structures made of tubulin dimers

long straight and rigid. hollow

Question 5

what tubulin genes are in microtubules

Answer 5

six a, seven b and also y

Question 6

describe the dimer arrangement in microtubules

Answer 6

head to tail; polarised + and - ends

Question 7

what does MTOC stand for

Answer 7

microtubule organising centre

Question 8

describe the 5 stages of MT growth as part of the centrosome

Answer 8

located next to nucleus
plus end grow out of this
duplicates in interphase- each half a duplicated centriole pair
centrosomes move to opposite sides of the nucleus
during mitosis form the mitotic spindle

Question 9

what is dynamic instability in MTs

Answer 9

some MTs stop growing suddenly and shrink back rapidly

Question 10

what are the two MT forms and what caises them

Answer 10

t form- GTP bound

d form- GDP bound- less strong

Question 11

what does MAPs stand for

Answer 11

microtubule associated protein

Question 12

what are the two types of MAPs

Answer 12

stabilisers/structural and motors

Question 13

what are three types of MAP motors

Answer 13

mysoin
kinesin
dyein

Question 14

what do MAP motor proteins do

Answer 14

bind to polarised filaments (actin and microtubules) using ATP hydrolysis

Question 15

how are the different MAP motor proteins differentiated (3)

Answer 15

cargo they move
direction of movement
filaments they bind to

Question 16

what is the direction of kinesin and dyein

Answer 16

to plus end

to minus end

Question 17

what are 4 things that kinesin consists of

Answer 17

two helical heavy chains that dimerise to form a stalk
two light chains which are flexible
a tail that interacts with cargo
two globular ends that interact with microtuble and ATP

Question 18

describe two features of dyein

Answer 18

forms a large macromolecular assembly

are used for the beating of cilia and flagella

Question 19

what are cilia and flagella made of and what do they consist of

Answer 19

microtubules and dyeins and bundles of microtubules

Question 20

what are axonemes

Answer 20

conserved in evolution

9 special doublet microtubules one complete and one half- fused

Question 21

describe the movement of axoneme

Answer 21

action same for cilia or flagella
requires ATP
sliding of microtubules prevented by protein links
therefore movement causes bending

Question 22

what is actin

Answer 22

helical plymers of monomers of glubular actin

Question 23

what are three things G-actin can exist as

Answer 23

atp-actin adp-pi-actin or gdp-actin

Question 24

how is an actin protofilament formed

Answer 24

from a linear chain of subunits

Question 25

how do protofilaments form actin

Answer 25

two protofilaments of actin subunits then twist arounf each other to form actin filament

Question 26

what are the two end types filaments have

Answer 26

pointed and barbed

slow dissociated and get addition of monomers

Question 27

what happens as actin ages

Answer 27

atp-actin hydrolyses to adp-pi-actin anf then phosphate released to form adp-actin

Question 28

what are three forms of f-actin

Answer 28

meshwork
tight parallel bundle
contractile bundle

Question 29

are there more proteins for microtubules or actin

Answer 29

actin

Question 30

name three species in which you get intermediate filaments

Answer 30

vertebrates, nematodes, molluscs

Question 31

what is the structure of intermediate filaments

Answer 31

elongated molecules with a central helical domain that forms a coil-coil with another molecule in same direction - pair then form a rope like structure