Cytoskeleton

Question 1

What is the cytoskeleton?

Answer 1

A filamentous structure found throughout the cytoplasm

Question 2

What is the cytoskeleton formed of?

Answer 2

Protein monomers which assemble into repeat structures

Question 3

What 3 types of filaments are found in the cytoskeleton?

Answer 3

Actin
Microtubules
Intermediate filaments

Question 4

What is the main property of the cytoskeleton?

Answer 4

It is dynamic - can assemble and disassemble rapidly to suit the cells needs

Question 5

What is the function of the cytoskeleton?

Answer 5

To provide stability and support to the cell

Question 6

What can link to the cytoskeleton?

Answer 6

Other cellular components

Question 7

What are motor proteins?

Answer 7

Proteins that move organelles along filaments and filaments against each other

Question 8

What is the diameter of an actin filament?

Answer 8

5-9nm

Question 9

What are actin filaments made of?

Answer 9

Actin = globular protein

- Actin assembles into two stranded helical polymers

Question 10

What can actin helical polymers form?

Answer 10

3D gels
2D networks
Bundles - by lining up

Question 11

What are the functions of actin filaments?

Answer 11

Shape

Motility

Question 12

Where are actin filaments found?

Answer 12

Throughout the body but mainly concentrated beneath the cortex

Question 13

What is the diameter of a microtubule?

Answer 13

25nm

Question 14

What are microtubules made of?

Answer 14

Tubulin = globular protein containing alpha and beta subunits
- Long and straight

Question 15

What structure does tubulin form in microtubules?

Answer 15

Hollow tubes

Question 16

How do microtubules compare to actin filaments in terms of rigidity?

Answer 16

More rigid

Question 17

What are microtubules typically attached to?

Answer 17

Centrosomes at one end

Question 18

What is a centrosome?

Answer 18

A microtubule organising centre

Question 19

What does the end of the microtubule not attached to the centrosome do?

Answer 19

Grow and shrink

Question 20

What are the functions of microtubules?

Answer 20

Positioning of organelles
Mitosis
Intracellular transport

Question 21

What is the diameter of an intermediate filament?

Answer 21

10nm

Question 22

What is the function of intermediate filaments?

Answer 22

Mechanical support

Question 23

What are intermediate filaments made of?

Answer 23

Various intermediate filament proteins which are individually filamentous

Question 24

What are dimers within intermediate filaments?

Answer 24

Extended alpha helical regions which are wound together

Question 25

What are tetramers and how are they formed?

Answer 25

Soluble subunits formed by the association of dimers

Question 26

What to tetramers wind to form?

Answer 26

Rope-like fibres

Question 27

How is the cytoskeleton formed?

Answer 27

Monomers form end-to-end and side-to-side interactions that are non-covalent and therefore can be broken and formed easily for rapid assembly and disassembly

Question 28

What does the relative strength of end-to-end and side-to-side interactions formed between monomers determine?

Answer 28

Mechanical strength

Question 29

What is the rate of monomer addition relative to?

Answer 29

Monomer concentration

Question 30

What happens when there is a critical concentration of monomers?

Answer 30

There is no net growth

Question 31

What type of ends do actin filaments and microtubules have?

Answer 31

Fast and slow growing = + and -

Question 32

What additional proteins may be associated with nucleation?

Answer 32

Auxiliary proteins which may act as an initiator for a new filament

Question 33

What additional proteins may be associated with assembly?

Answer 33

Proteins which bind monomers depending on their relative concentration

Question 34

What additional proteins may be associated with disassembly?

Answer 34

Proteins which can bind and either stabilise or destabilise filaments

Question 35

What property of the cytoskeleton might toxins affect? Give two examples

Answer 35

Their ability to disassemble or control of actin filaments - taxol = stabilises microtubules - colchicine = binds free tubulin

Question 36

What is myosin?

Answer 36

An actin based motor protein

Question 37

How many myosin genes are there in a human?

Answer 37

40

Question 38

What type of myosin makes muscles contract?

Answer 38

Myosin II

Question 39

How are myosin long domains formed?

Answer 39

By the coiling of two mysoin II heavy chains

Question 40

What do tail domains interact with?

Answer 40

Other myosin parts forming large bipolar 'thick myosin'

Question 41

What do globular myosin heads contain?

Answer 41

Force generating machinery

Question 42

What are kinesin and dynein?

Answer 42

Microtubular motor proteins

Question 43

Which part of kinesin and dynein interacts with the cytoskeleton?

Answer 43

Myosin heads

Question 44

What way does kinesin move organelles?

Answer 44

From the - to the + end of the microtubule

Question 45

What way does dynein move organelles?

Answer 45

From the + to the - end of the microtubule

Question 46

Where in the cell is the golgi retained and what molecule is retained by?

Answer 46

Close to centrosomes by dynein

Question 47

Where in the cell is the ER dispersed and by what molecule?

Answer 47

To the cell periphary by kinesin

Question 48

How are vesicles moved within a cell?

Answer 48

Along microtubules | - From the golgi to ER by dynein

Question 49

What is cell crawling and what types of cells does it occur in?

Answer 49

The rearrangement of actin in the cytoskeleton - Macrophages - Neutrophils

Question 50

What are flagella and cilia and what are they composed of?

Answer 50

Tubular structures composed microtubules

Question 51

How do flagella and cilia move?

Answer 51

Ciliary dynein causes microtubules to slide across one another allowing the flagella/cilia to propel the cell forward

Question 52

What is found at the tip of microvilli?

Answer 52

Bundles of actin filaments

Question 53

How do microvili move?

Answer 53

Myosin attached to the cell membrane moves the actin filaments causing the microvili to 'wave'