lecture 12

Question 1

whats the basic unit that forms microtubules

Answer 1

tubulin

Question 2

whats the microtubule organization centre

Answer 2

centrosome

Question 3

how many protofilaments do microtubules have within the wall of the tubule

Answer 3

13

Question 4

where are microtubules found (4)

Answer 4

cytoskeleton
mitotic spindle
centrioles
core of cilia and flagella

Question 5

whats the structure of protofilaments (building blocks of microtubules)

Answer 5

they consist of one a-tubulin at the minus end and one b-tubulin at the plus end

Question 6

are microtubules polar or non polar

Answer 6

polar

Question 7

where do microtubules grow from

Answer 7

centrosomes (specialized microtubule organization centres)

Question 8

what does the centrosome contain

Answer 8

two barrel shaped centrioles

Question 9

what end of microtubules grow outwards into the cytosol

Answer 9

the + end

Question 10

what is dynamic instability

Answer 10

some of the microtubules of the cytoskeleton being subject to breakdown/weakness

Question 11

what determines the dynamic instability of microtubules

Answer 11

the capacity of tubulin dimers to hydrolyze GTP to GDP

Question 12

whats the structure of a tubulin dimer

Answer 12

1 GTP molecule tightly bound to B-tubulin

Question 13

where are GTP tubulin dimers added

Answer 13

the plus end of a microtubule

Question 14

what happens to growth if the tubulin dimers are added to the end of the microtubule faster than the GTP they carry is hydrolyzed?

Answer 14

growth happens

Question 15

what dimer bind stronger to neighbouring cells in microtubules

Answer 15

the GTP associated ones bind stronger over the GDP ones

Question 16

what happens when there are GDP tubulin dimers at the end of the + end of microtubules

Answer 16

the balance of the microtubule will favour disassembly

Question 17

what is catastrophic disassembly

Answer 17

when microtubules start to shrink rapidly and may even disappear

Question 18

what connects one dimer to the next (stabilizing protein)

Answer 18

Tau

Question 19

what are MAPS

Answer 19

stability and promoting proteins to help microtubules

Question 20

what do microtubules and actin filaments serve as tracks for

Answer 20

motor proteins

Question 21

what are the three categories of motor proteins

Answer 21

kinesin and dynein that travel along microtubules
myosin which travels along actin filaments

Question 22

which motor proteins are uni directional

Answer 22

kinesin and dynein

Question 23

where do kinesis move

Answer 23

towards the plus end of the microtubule

Question 24

where do dyneins move

Answer 24

towards the minus end of the microtubule

Question 25

what part of the motor protein binds to vesicles or organelles

Answer 25

tail of motor proteins

Question 26

what does each motor protein step require

Answer 26

the hydrolysis of a single ATP molecule

Question 27

what helps determine the cells shape

Answer 27

microtubule distribution

Question 28

what bind the ER and pulls it outwards along microtubules

Answer 28

kinesin

Question 29

what pulls the golgi inwardly along microtubules

Answer 29

dyneins

Question 30

what is a basal body

Answer 30

microtubule organizing centre that forms at the base of a cilia or flagellum

Question 31

what are basal bodies identical to in structure?

Answer 31

centrioles

Question 32

whats the internal structure of eukaryotic flagella or cilia

Answer 32

axoneme

Question 33

whats the arrangement of an axoneme

Answer 33

9 doublets and 2 singles

Question 34

what holds the two singles in an axoneme together

Answer 34

radial spokes

Question 35

what generates the bending motion of the cilium/flagellum

Answer 35

dynein

Question 36

what causes doublets to slide against each other

Answer 36

dyneins power stroke

Question 37

why does dyneins power stroke cause a bend

Answer 37

there are multiple links around microtubule doublets and the power stroke causes a bend instead