Cytoskeleton

Question 1

What are the functions of the cytoskeleton?

Answer 1

• Maintains shape of cells
• Moves intracelular traffic
• Pulls chromosomes apart in mitosis

Question 2

What are the 3 types of filament in the cell from smallest to largest?

Answer 2

• Microfilaments (7-9nm)
• Intermediate filaments (10nm)
• Microtubules (25nm)

Question 3

What are microfilaments also known as?

Answer 3

Actin filaments
- Polymers of actin

Question 4

What filament are microvilli formed by?

Answer 4

Microfilaments (actin filaments)

Question 5

What is the basic unit of the muscle fibre?

Answer 5

Sarcomere

Question 6

What 3 main structures make up the sarcomere?

Answer 6

Actin and associated proteins
- Thin filament

Myosin
- Thick filament

Z disc
- Contains vimentin and desmin

Question 7

What happens when myosin filaments slide past actin?

Answer 7

Contraction

Question 8

What is the main function of intermediate filaments?

Answer 8

Maintain cell shape / structure

Question 9

How can intermediate filaments help in cancer diagnosis?

Answer 9

Used as tumour markers

Question 10

What is immunohistochemical staining?

Answer 10

Antibodies are directed against intermediate filament proteins
- Specific filaments will be associated with certain tumour types
- Stain will show whether antibody binds
- Positive stain will suggest tumour origin/type

Question 11

What tissues are derived from mesenchymal tissue?

Answer 11

• Connective/soft tissue
• Fibroblasts
• Skeletal muscle
• Mesothelium lining of perineum, synovial joints
• Endothelium
• Adipocytes
• Osteoblasts

Question 12

Vimentin is found in what types of tissue?

Answer 12

Mesenchymal tissue

Question 13

What does the z disc contain?

Answer 13

Vimentin and desmin

Question 14

What are sarcomas?

Answer 14

Cancers of mesenchymal origin

Question 15

What tissue marker will sarcomas be +ve for?

Answer 15

Vimentin

Question 16

Leiomyosarcoma is a cancer of what tissue?

Answer 16

SM

Question 17

Liposarcoma is a cancer of what tissue?

Answer 17

Adipocytes

Question 18

What non-sarcoma tumors will be vimentin +ve?

Answer 18

• RCC
• Meningioma
• Endometrial carcinoma

Question 19

What part of the sarcomere can act as a tumor marker for muscle tumors?

Answer 19

Desmin

Question 20

What sarcomas may have a desmin +ve tumor?

Answer 20

• Rhabdomyosarcoma
• Leiomyoma
• Leiomyosarcoma

Question 21

Epithelial tumours most commonly have what tumour marker?

Answer 21

Keratin
- Cytokeratin

Question 22

What part of the cell do lamins (intermediate filament) form?

Answer 22

Nuclear envelope
- Contians outer and inner membrane with an intermembrane space

Question 23

What is a laminin?

Answer 23

Extracellular protein
- DIFFERENT FROM A LAMIN which forms the nuclear membrane

Question 24

Where are neurofilaments found?

Answer 24

Neurons (especially axons)

Question 25

What tumours may have a +ve neurofilament dtaining?

Answer 25

CNS tumors - Neurobalstoma - Medulloblastoma - Retinoblastoma

Question 26

What are GFAP (glial fibrillary acidic proteins) found in?

Answer 26

- Atrocytes (mainly) - other CNS glial cells (not neurons)

Question 27

What CNS tumours may have a positive GFAP marker?

Answer 27

- Astrocytoma - Glioblastoma

Question 28

What makes up a microtubule?

Answer 28

Alpha and Beta tubulin - They polymerize into a long 'protofilament' - Each dimer has 2 GTP

Question 29

Which GTP can be hydrolyzed on the microtubule?

Answer 29

Beta GTP - The alpha tubulin is simply part of the struacture and therefore cannot be used for energy

Question 30

Where do microtubules grow from on the cell?

Answer 30

Centrosome near nucleus - Emanate a star pattern on the cell

Question 31

Where is the negative and positive end of the MTs?

Answer 31

- Positive ends are at periphery - Negative end is at centrosome

Question 32

What is dynamic instability in relation to MTs?

Answer 32

Where microtubules grow slowly yet can rapidly disassemble (~ 100 times faster)

Question 33

What are the MT motor proteins called?

Answer 33

Dynein and kinesin

Question 34

What MT motor protein carries things away from the nucleus, towards +ve end?

Answer 34

Kinesin

Question 35

What MT motor protein carries tthings toward negative end?

Answer 35

Dynein

Question 36

What MT motor protein is responisble for the localization of the golgi apparatus near the cell centre?

Answer 36

Dynein

Question 37

What 2 motility structures are built from MTs and dynein?

Answer 37

Cilia and flagella

Question 38

How are axonemes arranged? Found in cilia and flagella

Answer 38

9x2 pattern - 9 doublet MTs in a ring - Surround a pair (2) MTs

Question 39

What are the cilia and flagella secured by?

Answer 39

Basal body - 9 groups of fused triplets of microtubules (no central pair)

Question 40

How do the cilia and flagella move?

Answer 40

- Through axonemal dynein: forms bridges between MTs - Activated dyenein pulls on neighbouring doublets - Sliding of doublets -> bending of cilia/flagella

Question 41

What does cilia and flagella need to activate dynein and therefore move?

Answer 41

ATP (MT dependent ATPase)

Question 42

Primary cilia dyskinesia (PCD) is due gene mutations coding for what?

Answer 42

Dynein

Question 43

Primary ciliary dyskinesia (mutated dynein) results in what?

Answer 43

- Rhinosinusitis -> pneumonia - Infertility

Question 44

What is Kartagener's syndrome? (the triad of symptoms, associated with PCD)

Answer 44

- Chronic sinusitis - Bronchiectasis (chronic cough, recurrent infections) - Situs inversus

Question 45

What is the mitotic spindle made up of?

Answer 45

MTs

Question 46

What cancer drugs inhibit MTs?

Answer 46

- Vincristine, vinblastine (inhibit polymerisation) - Paclitaxel (enhance polymerisation, block breakdown)

Question 47

How does colchicine inhibit MTs?

Answer 47

Prevents MT assembly - Disrupts chemotaxis, generation of cytokines, phagocytosis

Question 48

What anti-gout medication prevents MT assembly?

Answer 48

Colchicine

Question 49

What ant-fungal drug inhibits MTs?

Answer 49

Griseofulvin

Question 50

What ant-helminth medication inhibits MTs?

Answer 50

Mebendazole