L4 cytoskeleton

Question 1

describe structure of myosin

Answer 1

thick protein filament with tail and 2 head groups

Question 2

describe structure of actin

Answer 2

thin filament of globular subunits

Question 3

what is the function of actin

Answer 3

define cell shape
allows cells to change shape
allows cell movement
allows cells to exert contractile force (eg in cell division)

Question 4

where in the cell are actin filaments located?

Answer 4

(inside cell) around perimeter as if lining

Question 5

explain the polymerisation of actin

Answer 5

the filaments undergo dynamic polymerisation - depolymerisation to allow shape changes 
they can be : 
   severed
   cross linked 
   bundled up

Question 6

what are intermediate filaments made from in
epithelia
nerve cells

Answer 6

keratin ,

neurofilaments

Question 7

functions of intermediate filaments

Answer 7

strengthen cells against mechanical stress
structural support of nuclear envelope
allow stretching of epithelium

Question 8

what are the intermediate filaments that support the nuclear envelope made from

Answer 8

nuclear lamins

Question 9

where in the cell are intermediate filaments located

Answer 9

they come from either side

also around nucleus

Question 10

what is the mitotic spindle composed of

Answer 10

microtubules -
1. dimer of a and B tubulin forms a protofilament
2. 13 protofilaments form the tubule
3. the plus end ends with B tubulin which polymerises
faster, the minus end ends with a tubulin

Question 11

functions of microtubules

Answer 11

form spindle during cell division
form cilia and propel cilia movement
form network in cytoplasm to help organelle movement

Question 12

where are microtubules located in cell

Answer 12

around centrosome

throughout cell

Question 13

examples of 2 motor proteins

Answer 13

kinesin

dyneins

Question 14

function of kinesin

Answer 14

moves vesicles toward plus end of microtubule (to right)

Question 15

function of dynein

Answer 15

move vesicles toward minus end of microtubules (left)

Question 16

what other functions do motor proteins have

Answer 16

1. enable cilia/flagella to beat for movement
2. transport in neurons
3. can work on actin filaments to generate contractile force

Question 17

how do motor proteins move

Answer 17

using ATP

Question 18

what is the difference between the plus and minus end of a microtubule

Answer 18

plus end ends with B tubulin
minus end ends with a tubulin

B tubulin polymerises faster

Question 19

example of 3 actin based structures

Answer 19

1. stress fibres
2. lamellipodium
3. filopodium

Question 20

2 examples of intermediate filaments and where theyre found

Answer 20

1. keratin in skin

2. neurofilaments in nerve cells

Question 21

put the cytoskeleton elements into order of thickness smallest to biggest

Answer 21

actin filaments
intermediate filaments
microtubules

Question 22

explain formation of IFs

Answer 22

monomers form dimers which form tetramers

8 tetramers = filament

Question 23

is myosin 1 or 2 involved in contraction

Answer 23

2

Question 24

is the plus or minus end of a neuron towards the synapse?

Answer 24

plus

Question 25

what is needed for axonal transport towards the synapse

Answer 25

microtubules and kinesin

Question 26

what proteins regulate dynamics of actin filaments

Answer 26

slingshot proteins

Question 27

microvilli consist of what monomers ?

Answer 27

actin

Question 28

what does myosin 1 activity on actin filaments promote

Answer 28

transport of vesicles /organelles