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FMS > [FMS] CBS - cytoskeleton > Flashcards

[FMS] CBS - cytoskeleton Flashcards

1
Q

what is the cytoskeleton?

A

network of protein filaments in cell

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2
Q

what 3 things is the cytoskeleton composed of?

A
  • Actin microfilaments
  • Intermediate filaments
  • Microtubules
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3
Q

how are actin filaments formed?

A

formed by the polymerisation of globular proteins (g-actin) to make long, thin strands called filamentous actin (f-actin)using ATP hydrolysis. 2 filament actin then tightly bind together to make actin

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4
Q

what is the structure of actin?

A

double helix

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5
Q

what is the diameter of actin?

A

7-9nm

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6
Q

where does g actin bind during the polymerisation of actin?

A

g actin binds in a head-to-tail fashion, ie head of one attaches to tail of another

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7
Q

can monomers be added to both the +ve and -ve end of an actin filament

A

yes

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8
Q

4 functions of actin

A
  • Muscle contraction
  • Mechanical support
  • Maintaining cell shape
  • Cell movement
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9
Q

what cell is an example of Mechanical support

A

micro villi

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10
Q

what are the 3 actin binding proteins?

A
  • G actin binding proteins
  • Cross-linking proteins
  • Severing
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11
Q

give an example of a G actin binding protein and what it does

A

– thymosin β4 : inhibits polymerisation

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12
Q

give 2 examples of cross linking proteins and what it does

A

– villin : parallel bundles in microvilli
– filamin : joining at angles to create a
mesh

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13
Q

give an example of a severing protein and what it does?

A

– gelsolin : cuts and binds (+) end; the
other part depolmerises – “gel to sol”

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14
Q

how is actin polymerised?

A

via NON-COVALENT interactions

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15
Q

what is present in non-muscle cells?

A

Muscle myosin

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16
Q

the interaction between what allows movement? and what does it require

A

Interaction between myosin and actin microfilaments allow movement ,
requires ATP hydrolysis

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17
Q

what allows movement within cells?

A

cytokinesis

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18
Q

describe how movement occurs WITHIN CELLS

A

via CYTOKINESIS

- ring of *actin* forms in cell centre anchoring to the *plasma membrane*
- *myosin* contracts and constricts the cell
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19
Q

What allows movement of cells outside the cells?

A

lamellipodia

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20
Q

explain Lamellipodia formation

A

Lamellipodia formation:

generated by rapid growth of actin filament at cell membrane

tip of lamellipodia interacts with ECM by integrins

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21
Q

what is an intermediate filament?

A

they are polymers of individual IF proteins

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22
Q

how are IF proteins formed?

A
  • helical dimer forms
  • 2 helical dimers combine to form tetramer
  • tetramers link together in a staggered formation to make a filament
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23
Q

whats the diameter of an IF protein?

A

10nm

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24
Q

3 examples of IF binding proteins?

A

Epithelia cells
Axons
Universal (nuclear)

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25
Q

example of epithelia cells and what it does

A

Epithelia cells : keratin(s)
* Physical support and external structures

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26
Q

example of axons and what it does

A

– Axons : neurofilamin(s)
* Structural arrangement of axons

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27
Q

example of universal (nuclear) protein and what it does

A

– Universal (nuclear) : lamins A, B, C
* Supporting nuclear structure

28
Q

How do IF’s interact with the cytoskeleton?

A

IFs can link actin mircofilaments and also microtubules e.g. plectin

29
Q

what is the keratin mutation disease called?

A

epidermolysis bullosa simplex (EBS)

30
Q

what is the name of the disease caused by neurofilament abnormal expression?

A

neurodegenerative disease amyotrophic lateral sclerosis (ALS)

31
Q

whats a microtubule made from?

A

protofilaments

32
Q

formation of a microtubule:

A

formation of a microtubule:

a tubulin and b tubulin assemble to make a heterodimer these dimers then associate to make a protofilament

33
Q

how many protofilaments make a microtubule, how are they arranged?

A

13, arranged in PARALLEL

34
Q

where on the protofilament can monomers be added on a microtubule?

A

both the +ve and -ve end

35
Q

whats the diameter of a microtubule?

A

25nm

36
Q

whats the name for the place that microtubules ‘grow’ out of?

A

MTOC (Microtubule-Organising Centre) - Microtubules “grow out” from
MTOC until reach destination and
then are stabilised

37
Q

out of actin, IFs and Microtubules which ones are dynamic and non-dynamic?

A

dynamic = can be added/ removed from both ends (positive and negative)
non-dynamic = can only be added/removed from ONE END (either positive or negative)

actin = DYNAMIC
IFs = NON-DYNAMIC
Microtubules = DYNAMIC

38
Q

Even though IFs are non-dynamic, theres one exception to this, what is it and why?

A

Lamins are dynamic as nuclear membrane reforms during mitosis

39
Q

why are IFs not dynamic?

A

theyre more stable - involved in structural stability to maintain the scaffold and dont need to be assembled/disassembled as much as actin and microtubules

40
Q

how many MTOCs are there per nucleus?

A
  • one MTOC associated with a nucleus
41
Q

what does MTOC stand for?

A
  • microtubule organizing center
42
Q

what are the 5 functions of microtubules?

A
  1. dynamic scaffold : spindle for chromatid separation in mitosis
  2. movement of cargo to specific cell locations
  3. central internal cilia support
  4. stabilises cell structure - platelets
  5. organisation of organelle structure - ER
43
Q

how does spindle formation occur

A

spindle formation

  • made up of microtubules
  • formation initiated from centrosome
  • centrosome has centrioles (pair) which have stable fused microtubules
  • centrosomes form at cell poles
44
Q

kinesin moves towards the ___ end

A

positive - towards the cell periphery (out)

45
Q

dynein moves towards the ___ end (in)

A

negative - near the nucleus

46
Q

what process moves cargo along the microtubule

A

atp hydrolysis

47
Q

what is cilia

A

Membrane bound hair-like extensions

48
Q

what is the MTOC called and where is located?

A

MTOC is called Basal Body located close to membrane

49
Q

when is cilia disassembled?

A

mitosis

50
Q

what are the 2 specialised types of cilia and what do they do>

A

stereo cilia, motile cilia

  • Stereocilia in the inner ear – sound detection
  • Motile cilia in respiratory / lung ciliated epithelia beat and move fluid around
51
Q

is cilia dynamic or non dynamic?

A

dynamic - disassembled in mitosis

52
Q

how does stereocilia work?

A

The cells are depolarised or
hyperpolarised by deflections caused by sound

53
Q

how is stereocilia kept rigid?

A

by actin filaments

54
Q

2 types of ciliopathies

A
  • Situs inversus
  • Autosomal Dominate Polycystic Kidney Disease (ADPKD)
55
Q

what is situs inversus

A
  1. inherited organs on wrong side
  2. defect in cilia-mediated movement of growth factor in embryo
56
Q

what is ADPKD - Autosomal Dominate Polycystic Kidney Disease

A
  1. formation of kidney cystic expand = normal tissue disrupted
  2. mutated proteins (polycystin-1 and -2) associated with abnormal function of primary cilia
57
Q

2 types of Anti-cancer chemotherapeutic agents

A

Colchicine : binds tubulin monomers prevents microtubule formation

Taxol : binds and stabilises microtubules

58
Q

whats the name of the 2 junctions between cells that are connected to the cell cytoskeleton

A

– desmosome
– gap junctions

59
Q

whats the name of the 2 attachments to the ECM that are connected to the cell cytoskeleton

A
  • hemidesmosomes
    – focal adhesions
60
Q

what disease is caused by a mutation in the Lamin A gene

A

Hutchinson – Guilford Progeria Syndrome (HGPS)

61
Q

what happens when there’s a mutation in the Lamin A gene

A

Results in the synthesis of progerin (abnormal lamin A protein) so patients have premature ageing features

62
Q

do cytoskeleton quiz on keats then come back

A

https://keats.kcl.ac.uk/mod/quiz/view.php?id=7540185

63
Q

where does mediated cell movement in the Lamellipodia occur?

A

Extra Cellular Matrix

64
Q

….. microtubules attach to centromere of chromatid

A
  • KINETOCHORE microtubules attach to centromere of chromatid
65
Q

…. microtubules attach centrosome to cell membrane

A

ASTER microtubules attach centrosome to cell membrane

FMS (33 decks)

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