Lecture 15 and 16

Question 1

What is the diameter of microtubules?

Answer 1

25nm outer

15nm inner

Question 2

What are the monomers of microtubules?

Answer 2

alpha and beta tubulin

Question 3

What is the diameter of microfilaments?

Answer 3

7nm

Question 4

What are the monomers of microfilaments?

Answer 4

G actin

Question 5

What is the diameter of intermediate filaments?

Answer 5

8-12nm

Question 6

Name some intermediate filaments.

Answer 6

Keratins, vimentin, desmin, nuclear lamins

Question 7

What are the two types of microtubules?

Answer 7

Cytoplasmic and axonemal

Question 8

What do cytoplasmic microtubules do?

Answer 8

Regulation of cell shape
Formation of mitotic spindle
Vesicle transport

Question 9

What do axonemal microtubules do?

Answer 9

Cell motility and signalling hub

Question 10

Where are axonemal microtubules found?

Answer 10

Basal bodies, cillia, flagella

Question 11

What are the three stages of microtubule polymerisation?

Answer 11

Nucleation, elongation, plateau (treadmilling)

Question 12

Microtubule growth is _____ dependent.

Answer 12

Concentration

Question 13

What is critical concentration?

Answer 13

The tubulin concentration at which MT assembly is balanced with dissaembly

Question 14

What is the name given to the model in which one population of MT’s grow and others shrink by depolymerization?

Answer 14

Dynamic instability

Question 15

What are the names given to the growth and shrinkage periods of MT’s?

Answer 15

Catastrophe and resuce

Question 16

What causes dynamic instability?

Answer 16

GTP cap is hydrolysed, leading to catastrophe

Question 17

What is the structure of a centriole?

Answer 17

Barrel shaped, 9 tubulin triplets, surrounded by pericentriole material

Question 18

Name 3 microtubule stabilizing/bundling proteins.

Answer 18

tau
MAP2
+-TIP proteins

Question 19

Name 3 microtubule detabilizing/severing proteins.

Answer 19

Stathmin/Op18
Catastophins
Katanins

Question 20

Name two MT inhibiting drugs.

Answer 20

Colchicine (promotoes disassembly)

Nocodazole (inhibits MT assembly)

Question 21

What are 4 roles of microfilaments?

Answer 21

Muscle contraction
Intracellular tension/cell shape
Cell migration (lamellar and amoeboid movement)
Cytoplasmic transport

Question 22

What are the types of monomer that make up microfilamnets?

Answer 22

Alpha actin (muscle specific)
Beta and gamma actin (all cells)

Question 23

What protein binds ATP actin and promotes polymerisation/

Answer 23

Profilin

Question 24

What protein binds ATP actin and blocks polymerisation?

Answer 24

Thymosin

Question 25

What protein promotes nucleation and branching in actin filaments?

Answer 25

Arp2/3

Question 26

What do formins do?

Answer 26

Bind actin filaments and promote elongation

Question 27

What do capping protiens do?

Answer 27

Binds the end of a filament and prevent further loss/addition of subunits (e.g. CapZ)

Question 28

What binds G-actin and F-actin and also severs filaments?

Answer 28

ADF/cofilin

Question 29

What receptors ljnk cells to the extracellular matrix?

Answer 29

Integrin

Question 30

What receptors link cells to other cells?

Answer 30

Cadherin

Question 31

What are two classes of cadherin?

Answer 31

Adherens junctions (link to microfilamnets) and desmosomes (link to intermediate filaments)

Question 32

What are the two major eukaryotic motility systems?

Answer 32

Interactions between motor proteins and microtubules | Interactions between actin and myosin motor proteins

Question 33

What proteins transport towards the minus end of MTs

Answer 33

Dynein

Question 34

What proteins transport towards the plus end of MTs?

Answer 34

Kinesins

Question 35

What three parts do kinesins consist of?

Answer 35

Globular head Coiled helical region Light chain region

Question 36

How do kinesins move?

Answer 36

Walk: ATP hydrolysis brings foot to bind new beta-tubulin subunit

Question 37

How long are cilia?

Answer 37

2-10 micrometers

Question 38

How long are flagella?

Answer 38

10-200 micrometers

Question 39

What name is given to the shared structure of cilia and flagella?

Answer 39

Axoneme

Question 40

What is the structure of the axoneme?

Answer 40

9+2 structure, separated by 9 dynein molecules

Question 41

How does dynein generate bending of cilia/flagella?

Answer 41

Sliding microtubule model: ATP hydrolysis of denein

Question 42

How many types of myosins are there?

Answer 42

24

Question 43

What myosin doesn't move towards the plus end of f-actin?

Answer 43

myosin VI

Question 44

Which myosin walks along actin?

Answer 44

Myosin II

Question 45

What three proteins do thin filaments in muscles contain?

Answer 45

F-actin, tropomyosin and troponin

Question 46

Why is muscle contraction calcium dependent?

Answer 46

Calcium binds to a protein on tropomyosin, which changes conformation to reveal myosin binding site

Question 47

What is the prokaryotic homologue to tubulin?

Answer 47

FtsZ protein (involved in division regulation)

Question 48

What is the bacterial relative of the intermediate filament?

Answer 48

Crescentin (cell shape)

Question 49

What is similar to actin microfilaments in bacteria?

Answer 49

MreB protein (cell shape)