Cytoskeleton

Question 1

What is the cytoskeleton?

Answer 1

A dynamic, complex, intracellular network of tubules, filaments and fibres found in all eukaryotes

Question 2

What is the cytoskeleton made up of?

Answer 2

• Microtubules
• Microfilaments/Actin filaments
• Intermediate filaments
• Associated proteins
  (apart from in fungi)

Question 3

What are the roles of microtubules?

Answer 3

• Determine position of membrane enclosed organelles
• Direct intracellular transport
• Form mitotic spindle that segregates chromosome

Question 4

What are the roles of actin filaments?

Answer 4

• Determine shape of cell’s surface
• Necessary for whole cell locomotion
• Drive cytokinesis

Question 5

What is the function of intermediate filaments?

Answer 5

Provide mechanical support

Question 6

What are microtubules composed of?

Answer 6

Protofilaments: α and ß tubulin

Question 7

What does MAP stand for? What do they do?

Answer 7

Microtubule associated protein

Either chop microtubules to promote disassembly or bind to side of microtubule to stabilise it

Question 8

What types of microtubules are there?

Answer 8

• Cytoplasmic microtubules
• Special structures
• Stable and labile

Question 9

Dynamic instability

Answer 9

When the [GTP] is too high. The GTP-capped end can be accidentally hydrolysed –> rapid shrinkage from previous ‘+’ end

Question 10

What is an organising centre?

Answer 10

Pair of centrioles embedded in sea of proteins with nucleating sites/gamma tubule ring complexes

Question 11

What is another name for the organising centre?

Answer 11

Centrosome

Question 12

What does every microtubule grow out of?

Answer 12

The gamma-tubuling ring on a centrosome

Question 13

What is found within the mass of centriole material?

Answer 13

Basal bodies (these help to form spindles)

Question 14

Give examples of motor proteins

Answer 14

Dynein and kinesin

Question 15

In monomeric form what does actin have bound to it?

Answer 15

ATP

Question 16

When in filament form, what does actin have bound to it?

Answer 16

ADP

Question 17

What is the function of the actin filament association protein profilin?

Answer 17

Promotes assembly

Recruits actin monomers for polymerisation at plus end

Question 18

What is the function of the actin filament association protein thymosin?

Answer 18

Inhibits assembly

Binds actin monomers and prevents them from adding to plus end

Question 19

What is the function of the actin filament association protein gelsolin?

Answer 19

Sits on end to stop growing

Question 20

What is the function of the actin filament association protein fimbrin?

Answer 20

Responsible for close packing of actin filaments/bundling

Question 21

Subunits of intermediate filaments

Answer 21

I and II - epithelial keratins
III - desmin in muscle
IV - neurofilaments
V - nuclear lamins

Question 22

Which actin filament association protein sits on the end to stop growing?

Answer 22

Gelsolin

Question 23

Which actin filament association protein inhibits assembly?

Answer 23

Thymosin

Question 24

Which actin filament association protein promotes assembly?

Answer 24

Profilin

Question 25

Which actin filament association protein is responsible for bundling?

Answer 25

Fimbrin

Question 26

What is an example of clinical condition that is associated with disturbances in cytoskeletal function?

Answer 26

ALS, or amyotrophic lateral sclerosis, is a progressive neurodegenerative disease that affects nerve cells in the brain and the spinal cord