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USMLE Biochemistry > Cytoskeleton > Flashcards

Cytoskeleton Flashcards

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USMLE® Step 1 flashcards
1
Q

What are the functions of the cytoskeleton?

A
  • Maintains shape of cells
  • Moves intracelular traffic
  • Pulls chromosomes apart in mitosis
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2
Q

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

A
  • Microfilaments (7-9nm)
  • Intermediate filaments (10nm)
  • Microtubules (25nm)
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3
Q

What are microfilaments also known as?

A

Actin filaments
- Polymers of actin

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4
Q

What filament are microvilli formed by?

A

Microfilaments (actin filaments)

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5
Q

What is the basic unit of the muscle fibre?

A

Sarcomere

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6
Q

What 3 main structures make up the sarcomere?

A

Actin and associated proteins
- Thin filament

Myosin
- Thick filament

Z disc
- Contains vimentin and desmin

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7
Q

What happens when myosin filaments slide past actin?

A

Contraction

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8
Q

What is the main function of intermediate filaments?

A

Maintain cell shape / structure

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9
Q

How can intermediate filaments help in cancer diagnosis?

A

Used as tumour markers

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10
Q

What is immunohistochemical staining?

A

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

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11
Q

What tissues are derived from mesenchymal tissue?

A
  • Connective/soft tissue
  • Fibroblasts
  • Skeletal muscle
  • Mesothelium lining of perineum, synovial joints
  • Endothelium
  • Adipocytes
  • Osteoblasts
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12
Q

Vimentin is found in what types of tissue?

A

Mesenchymal tissue

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13
Q

What does the z disc contain?

A

Vimentin and desmin

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14
Q

What are sarcomas?

A

Cancers of mesenchymal origin

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15
Q

What tissue marker will sarcomas be +ve for?

A

Vimentin

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16
Q

Leiomyosarcoma is a cancer of what tissue?

A

SM

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17
Q

Liposarcoma is a cancer of what tissue?

A

Adipocytes

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18
Q

What non-sarcoma tumors will be vimentin +ve?

A
  • RCC
  • Meningioma
  • Endometrial carcinoma
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19
Q

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

A

Desmin

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20
Q

What sarcomas may have a desmin +ve tumor?

A
  • Rhabdomyosarcoma
  • Leiomyoma
  • Leiomyosarcoma
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21
Q

Epithelial tumours most commonly have what tumour marker?

A

Keratin
- Cytokeratin

22
Q

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

A

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

23
Q

What is a laminin?

A

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

24
Q

Where are neurofilaments found?

A

Neurons (especially axons)

25
Q

What tumours may have a +ve neurofilament dtaining?

A

CNS tumors
- Neurobalstoma
- Medulloblastoma
- Retinoblastoma

26
Q

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

A
  • Atrocytes (mainly)
  • other CNS glial cells (not neurons)
27
Q

What CNS tumours may have a positive GFAP marker?

A
  • Astrocytoma
  • Glioblastoma
28
Q

What makes up a microtubule?

A

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

29
Q

Which GTP can be hydrolyzed on the microtubule?

A

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

30
Q

Where do microtubules grow from on the cell?

A

Centrosome near nucleus
- Emanate a star pattern on the cell

31
Q

Where is the negative and positive end of the MTs?

A
  • Positive ends are at periphery
  • Negative end is at centrosome
32
Q

What is dynamic instability in relation to MTs?

A

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

33
Q

What are the MT motor proteins called?

A

Dynein and kinesin

34
Q

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

A

Kinesin

35
Q

What MT motor protein carries tthings toward negative end?

A

Dynein

36
Q

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

A

Dynein

37
Q

What 2 motility structures are built from MTs and dynein?

A

Cilia and flagella

38
Q

How are axonemes arranged?

Found in cilia and flagella

A

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

39
Q

What are the cilia and flagella secured by?

A

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

40
Q

How do the cilia and flagella move?

A
  • Through axonemal dynein: forms bridges between MTs
  • Activated dyenein pulls on neighbouring doublets
  • Sliding of doublets -> bending of cilia/flagella
41
Q

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

A

ATP (MT dependent ATPase)

42
Q

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

A

Dynein

43
Q

Primary ciliary dyskinesia (mutated dynein) results in what?

A
  • Rhinosinusitis -> pneumonia
  • Infertility
44
Q

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

A
  • Chronic sinusitis
  • Bronchiectasis (chronic cough, recurrent infections)
  • Situs inversus
45
Q

What is the mitotic spindle made up of?

A

MTs

46
Q

What cancer drugs inhibit MTs?

A
  • Vincristine, vinblastine (inhibit polymerisation)
  • Paclitaxel (enhance polymerisation, block breakdown)
47
Q

How does colchicine inhibit MTs?

A

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

48
Q

What anti-gout medication prevents MT assembly?

A

Colchicine

49
Q

What ant-fungal drug inhibits MTs?

A

Griseofulvin

50
Q

What ant-helminth medication inhibits MTs?

A

Mebendazole

USMLE Biochemistry (44 decks)

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