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Cytoskeleton & Cell Adhesion Flashcards

1
Q

How thick are microfilaments?

A

7nm

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2
Q

How thick are intermediate filaments?

A

10nm

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3
Q

What is the diameter of a microtubule?

A

25nm

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4
Q

What can microfilaments also be called? (2)

A

Actin filaments

F-actin

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5
Q

What are the subunits of microfilaments?

A

G-actin

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6
Q

What percentage of the total protein of the cell is comprised of microfilaments?

A

5%

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7
Q

How many subunits per complete turn of the microfilaments helix?

A

13 G-actin

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8
Q

What is the structure of a microfilament?

A

Polarised double helix

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9
Q

How long is one complete turn of the microfilament helix?

A

37nm

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10
Q

Why do microfilaments display polarity?

A

G-actin monomers are asymmetrical

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11
Q

What molecule is required for the growth of microfilaments?

A

ATP

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12
Q

On what end does microfilament growth/shortening occur fastest?

A

Plus end

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13
Q

What are the major functions of microfilaments? (3)

A

Mechanical support

Cell shape changes and maintenance

Cell motility

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14
Q

What do actin-sequestering proteins do?

A

Bind to G-actin to prevent polymerisation

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15
Q

What do capping proteins do?

A

Bind to ends of actin filaments to prevent growth (stabilisation)

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16
Q

What do motor proteins do?

A

Allow movement

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17
Q

What do cross-linking proteins do?

A

Hold actin cell cortex together

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18
Q

What kind of intermediate filaments are found in epithelia?

A

Keratin

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19
Q

What kind of intermediate filaments are found in neurons?

A

Neurofilamin/neurofilaments

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20
Q

What kind of intermediate filaments are found in nuclei?

A

Lamins

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21
Q

Where is the intermediate filaments network most dense usually?

A

Around the nucleus

22
Q

What are the functions of intermediate filaments? (3)

A

Provide rigidity

Anchor cells at some junctions

Support nuclear structure (and protect/attach chromatin)

23
Q

Describe the formation of intermediate filaments

A

One intermediate filament protein monomer = 2 intermediate filaments joined end-to-end

Two monomers come together to create a helical dimer

Two dimers combine = tetramer (fundamental unit)

Tetramers linked end-to-end in staggered formation

24
Q

What are the subunits of microtubules?

A

One alpha-tubulin and one beta-tubulin

25
Q

Which part of the microtubule subunit is positive?

A

Beta-tubulin

26
Q

How many subunits in a cross-section of a microtubule?

27
Q

What molecule is required for microtubule growth?

28
Q

At what end do changes in microtubule length occur fastest?

29
Q

What organelles do microtubules usually grow out of and in what orientation?

A

Centrioles

Minus end close to centrosome with plus end pointing to cell periphery

30
Q

What filament supports microvilli and stereocilia?

A

Microfilaments

31
Q

What are the functions of actin sheets in cells? (2)

A

Support in cell cortex

Maintains cell shape

32
Q

What parts of the cytoskeleton are present in axons?

A

Intermediate filaments

Microtubules (stabilise area close to synapse)

33
Q

What stabilises the processes of thrombocytes?

A

Microtubules

34
Q

What do microfilaments anchor?

A

Synaptic vesicles (close to presynaptic membrane)

35
Q

What organelle is organised by microtubules?

A

Endoplasmic reticulum

36
Q

Describe how cells move using actin.

A
  1. Cell pushed out protrusions in front (leading edge) via actin polymerisation
  2. Protrusions adhere to surface using focal adhesions (containing integrins)
  3. F-actin connects to focal adhesions
  4. Rest of cell pulls against anchorage points and drags itself forward
  5. Actin depolymerises at rear
37
Q

What are the two types of protrusions caused by actin polymerisation?

A

Lamellipodia (thick)

Filopodia (thin)

38
Q

What motor protein pulls on F-actin to drag the cell forward?

A

Myosin II (non-muscle)

39
Q

What cell structure is stabilised by microtubules?

40
Q

What MAP causes cilia movement and how do cilia move?

A

Dynein

Spiral movement

41
Q

What is used to transport synaptic vesicles along axons?

A

Microtubules

Kinesin (to plus end)

Dynein (to minus end)

42
Q

What part of the cytoskeleton do chemotherapeutic agents target and why?

A

Microtubules

Involved in movement of chromosomes/mitotic spindle

43
Q

How do colchicine and vinblastine work?

A

Destabilise microtubules (cut up)

44
Q

How does taxol work?

A

Stabilises microtubules (cannot change length to move chromosomes)

45
Q

What is caused by a mutation in the dystrophin gene?

A

Duchenne and Becker muscular dystrophy (actin)

46
Q

What is caused by a mutation in the myosin VII gene?

A

Usher’s syndrome (hereditary blindness and deafness) - actin/disrupts stereocilia

47
Q

What is caused by keratin gene mutations?

A

Epidermolysis bullosa symplex (skin highly sensitive to mechanical injury; blistering) - Intermediate filaments

48
Q

What is caused by plectin mutations?

A

Epidermolysis bullosa symplex with muscular dystrophy

49
Q

What causes Alzheimer’s disease?

A

Hyperphosphorylated Tau (MAP) builds up and cannot bind - microtubules

50
Q

What is caused by a mutation in the spastin gene?

A

Hereditary Spastic Paraplegia - microtubules (microtubule severing protein)

51
Q

How does Listeria bacteria hijack actin filaments?

A
  1. Listeria engulfed by host
  2. Bacterium escapes from phagocytic vesicle and divides
  3. F-actin polymerised at back of bacterium to give it motility
  4. Actin ‘comet’ drives bacterium into neighbouring cell
52
Q

How does the vaccinia virus use host cells?

A
  1. Virus engulfed by host
  2. Virus escapes phagocytic vesicle and divides
  3. Uses microtubules to be transported to cell periphery
  4. F-actin polymerised at back of virus
  5. F-actin comet drives virus into neighbouring cell

BMS02 (10 decks)

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