Cytoskeleton & Cell Adhesion Flashcards

(52 cards)

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
Which part of the microtubule subunit is positive?
Beta-tubulin
26
How many subunits in a cross-section of a microtubule?
13
27
What molecule is required for microtubule growth?
GTP
28
At what end do changes in microtubule length occur fastest?
Plus end
29
What organelles do microtubules usually grow out of and in what orientation?
Centrioles Minus end close to centrosome with plus end pointing to cell periphery
30
What filament supports microvilli and stereocilia?
Microfilaments
31
What are the functions of actin sheets in cells? (2)
Support in cell cortex Maintains cell shape
32
What parts of the cytoskeleton are present in axons?
Intermediate filaments Microtubules (stabilise area close to synapse)
33
What stabilises the processes of thrombocytes?
Microtubules
34
What do microfilaments anchor?
Synaptic vesicles (close to presynaptic membrane)
35
What organelle is organised by microtubules?
Endoplasmic reticulum
36
Describe how cells move using actin.
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
What are the two types of protrusions caused by actin polymerisation?
Lamellipodia (thick) Filopodia (thin)
38
What motor protein pulls on F-actin to drag the cell forward?
Myosin II (non-muscle)
39
What cell structure is stabilised by microtubules?
Cilia
40
What MAP causes cilia movement and how do cilia move?
Dynein Spiral movement
41
What is used to transport synaptic vesicles along axons?
Microtubules Kinesin (to plus end) Dynein (to minus end)
42
What part of the cytoskeleton do chemotherapeutic agents target and why?
Microtubules Involved in movement of chromosomes/mitotic spindle
43
How do colchicine and vinblastine work?
Destabilise microtubules (cut up)
44
How does taxol work?
Stabilises microtubules (cannot change length to move chromosomes)
45
What is caused by a mutation in the dystrophin gene?
Duchenne and Becker muscular dystrophy (actin)
46
What is caused by a mutation in the myosin VII gene?
Usher’s syndrome (hereditary blindness and deafness) - actin/disrupts stereocilia
47
What is caused by keratin gene mutations?
Epidermolysis bullosa symplex (skin highly sensitive to mechanical injury; blistering) - Intermediate filaments
48
What is caused by plectin mutations?
Epidermolysis bullosa symplex with muscular dystrophy
49
What causes Alzheimer’s disease?
Hyperphosphorylated Tau (MAP) builds up and cannot bind - microtubules
50
What is caused by a mutation in the spastin gene?
Hereditary Spastic Paraplegia - microtubules (microtubule severing protein)
51
How does Listeria bacteria hijack actin filaments?
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
How does the vaccinia virus use host cells?
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