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[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
example of epithelia cells and what it does
Epithelia cells : keratin(s) * Physical support and external structures
26
example of axons and what it does
– Axons : neurofilamin(s) * Structural arrangement of axons
27
example of universal (nuclear) protein and what it does
– Universal (nuclear) : lamins A, B, C * Supporting nuclear structure
28
How do IF’s interact with the cytoskeleton?
IFs can link actin mircofilaments and also microtubules e.g. **plectin**
29
what is the keratin mutation disease called?
epidermolysis bullosa simplex (EBS)
30
what is the name of the disease caused by neurofilament abnormal expression?
neurodegenerative disease amyotrophic lateral sclerosis (ALS)
31
whats a microtubule made from?
protofilaments
32
formation of a microtubule:
formation of a microtubule: *a* tubulin and *b* tubulin assemble to make a *heterodimer* these dimers then associate to make a *protofilament*
33
how many protofilaments make a microtubule, how are they arranged?
13, arranged in PARALLEL
34
where on the protofilament can monomers be added on a microtubule?
both the +ve and -ve end
35
whats the diameter of a microtubule?
25nm
36
whats the name for the place that microtubules 'grow' out of?
MTOC (Microtubule-Organising Centre) - Microtubules “grow out” from MTOC until reach destination and then are stabilised
37
out of actin, IFs and Microtubules which ones are dynamic and non-dynamic?
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
Even though IFs are non-dynamic, theres one exception to this, what is it and why?
Lamins are dynamic as nuclear membrane reforms during mitosis
39
why are IFs not dynamic?
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
how many MTOCs are there per nucleus?
- one MTOC associated with a nucleus
41
what does MTOC stand for?
- microtubule organizing center
42
what are the 5 functions of microtubules?
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
how does spindle formation occur
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
kinesin moves towards the ___ end
positive - towards the cell periphery (out)
45
dynein moves towards the ___ end (in)
negative - near the nucleus
46
what process moves cargo along the microtubule
atp hydrolysis
47
what is cilia
Membrane bound hair-like extensions
48
what is the MTOC called and where is located?
MTOC is called Basal Body located close to membrane
49
when is cilia disassembled?
mitosis
50
what are the 2 specialised types of cilia and what do they do>
stereo cilia, motile cilia - Stereocilia in the inner ear – sound detection - Motile cilia in respiratory / lung ciliated epithelia beat and move fluid around
51
is cilia dynamic or non dynamic?
dynamic - disassembled in mitosis
52
how does stereocilia work?
The cells are *depolarised* or *hyperpolarised* by deflections caused by sound
53
how is stereocilia kept rigid?
by actin filaments
54
2 types of ciliopathies
* Situs inversus * Autosomal Dominate Polycystic Kidney Disease (ADPKD)
55
what is situs inversus
1. inherited organs on wrong side 2. defect in cilia-mediated movement of growth factor in embryo
56
what is ADPKD - Autosomal Dominate Polycystic Kidney Disease
1. formation of kidney cystic expand = normal tissue disrupted 2. mutated proteins (polycystin-1 and -2) associated with abnormal function of primary cilia
57
2 types of Anti-cancer chemotherapeutic agents
Colchicine : binds tubulin monomers prevents microtubule formation Taxol : binds and stabilises microtubules
58
whats the name of the 2 junctions between cells that are connected to the cell cytoskeleton
– desmosome – gap junctions
59
whats the name of the 2 attachments to the ECM that are connected to the cell cytoskeleton
- hemidesmosomes – focal adhesions
60
what disease is caused by a mutation in the Lamin A gene
Hutchinson – Guilford Progeria Syndrome (HGPS)
61
what happens when there's a mutation in the Lamin A gene
Results in the synthesis of progerin (abnormal lamin A protein) so patients have premature ageing features
62
do cytoskeleton quiz on keats then come back
https://keats.kcl.ac.uk/mod/quiz/view.php?id=7540185
63
where does mediated cell movement in the Lamellipodia occur?
Extra Cellular Matrix
64
….. microtubules attach to centromere of chromatid
- **KINETOCHORE** microtubules attach to centromere of chromatid
65
…. microtubules attach centrosome to cell membrane
**ASTER** microtubules attach centrosome to cell membrane

FMS (33 decks)

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