Cytoskeletal System

Question 1

Cytoskeleton

Answer 1

It is a network of interconnected filaments and tubules extending through the cytosol
-It plays roles in cell movement and division
-It is dynamic and changeable
-Cell interior is highly structured

Question 2

Cytoplasmic microtubules

Answer 2

-Maintaining axons
-Formation of mitotic and meiotic spindles
-Maintaining or altering cell shape
-Placement and movement of vesicles
-Orientation of cellulose microfibrils during plant cell wall growth

Question 3

Axonemal microtubules

Answer 3

-Includes the organised and stable microtubules found in structures such as:
-Cilia
-Flagella
-Basal bodies to which cilia and flagela attach
-The axoneme, the central shaft of a cilium or flagellum, is a highly ordered bundle of MTs

Question 4

Microtubule structure

Answer 4

-Beta tubulin will always be N-terminal end that has a plus end
-Alpha tubulin will always be a C-terminal end that has a negative charge

Question 5

rate-limitng step of microtubules

Answer 5

formation of dimers is slowest steps

Question 6

Microtubule assembling

Answer 6

Question 7

Microtubule Treadmiling

Answer 7

+ and - ends have different critical concentrations
-Treadmiling: addition of subunits at the plus end, and removal from the minus end ( constant elongation and shortening)

Question 8

Dynamic instability model

Answer 8

One population of MTs grows by polymerisation at the plus ends, whereas another population shrinks by depolymerisation at the plus ends
-GTP gives stability and when there is no GTP, the dimer breaks down at plus end which is known as catastrophe

Question 9

Catastrophe

Answer 9

-Individual MTs can go through periods of growth and shrinkage; a switch from growth to shrinkage

Question 10

rescue

Answer 10

A sudden switch back to growth phase

Question 11

Catastrophe and rescue graph

Answer 11

Question 12

MTOC

Answer 12

Microtubule organising center
-Gamma tubulin binds to gamma-TuRC and stabilises Mt

Question 13

MTOC distribution

Answer 13

Anaphase I- Centrosome
Basal body

Question 14

Centrosomes

Answer 14

Composed of a triplet arrangement with 9 triplet microtubules being used to make a centriole

Question 15

Colchicine, colcemid

Answer 15

Binds B-tubulin
-inhibitng assembly

Question 16

Nocadazole

Answer 16

Binds beta-tubulin which inhibits polymerisation

Question 17

Vinblastine, vincristine

Answer 17

Aggregates tubulin heterodimers

Question 18

Paclitaxel (taxol)

Answer 18

Stabilises microtubules
-Uses up all tubulin causing cell to die because there is no movement

Question 19

MTOC different cells

Answer 19

Nerves
Ciliated epithelial
RBC

Question 20

Mt regulation

Answer 20

-great precision
-Mt-binding proteins use ATP to drive vesicle or organelle transport or to generate sliding forces between MTs
-Others regulate Mt structure

Question 21

Microfilament functions

Answer 21

-Smallest filaments
1. Muscle contraction
2. Cell migration, amoeboid movement and cytoplasmic streaming
3. Maintenance of cell shape
4. Structural core microvilli
5. Cleavage furrow production during cytokinesis

Question 22

G-actin

Answer 22

globular actin
single protein
gives rise to f-actin
-Has to be ATP-bound to be attached to filament

Question 23

F-actin

Answer 23

Filamentous actin
multiple G-actins bound together to form MF (polymerised)
-2 F-actin eind together to form MF

Question 24

Isoforms

Answer 24

alpha-actin-muscular
Beta-actin
gamma-actin

Question 25

Polarity of MF

Answer 25

Polarity is reflected in more rapid addition or loss of G-actin at plus end than minus end -After the G-actin monomers assemble onto MF, the ATP bound to them is slowly hydrolysed -So growing MF ends have ATP-actin whereas most of MF is composed of ADP-actin

Question 26

Architecture of Actin in crawling cells

Answer 26

-Rapid moving cells dont have stress fibers -The cell cortex, just beneath the plasma membrane, has actin crosslinked into a gel of MF

Question 27

Stress fibers

Answer 27

Cells that adhere tightly to underlying substratum have organised bundles called stress fibers -found in contractile bundle

Question 28

Cell cortex

Answer 28

gel

Question 29

Lamelllpodium

Answer 29

Branched network

Question 30

Flipodium

Answer 30

Parallel bundle

Question 31

Actin binding proteins

Answer 31

Control where and how actin assembles into MF

Question 32

Filament formation binding proteins

Answer 32

Monomer sequestering proteins prevent formation (thymosin) -Actin polymerising proteins cause formation (formin)

Question 33

Filament lenght binding proteins

Answer 33

filament-severing proteins (gelsolin) Filament-capping proteins (CapZ)

Question 34

Filament organisation actin binding proteins

Answer 34

Filament-crosslinking proteins (filamin) Filament-bundling proteins ( alpha-actin, fibrinin)

Question 35

Drugsthat affect stability of MFs

Answer 35

Question 36

Intermediate filaments

Answer 36

Most stable least soluble likely support entire cytoskeleton IF proteins are tissue specific -Keratin is NB component of structures that grow on skin in animals

Question 37

classes of IF

Answer 37

Question 38

IF formation

Answer 38

Question 39

Drugs that affect IF stability

Answer 39

Acrylamide- Causes loss of intermediate filament networks (carcinogenic)

Question 40

IF functions

Answer 40

Question 41

Critical concentration

Answer 41

The tubular heterodimer concentration at which MT assembly is exactly balanced with disassembly