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CELL BIOLOGY AND PHYSIOLOGY > week 4 - cytoskeleton > Flashcards

week 4 - cytoskeleton Flashcards

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1
Q

why does a vertebrate need a skeleton

A
  • Structure
  • Protection
  • Localisation
  • Movement
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2
Q

what does the cytoskeleton provide?

A
  • Structure
  • Protection
  • Localisation
  • Movement
  • Transport
  • communicaton
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3
Q

the cytoskeleton is a…

A

dynamic structure inside the cell

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4
Q

the cytoskeleton allows cells to…

A

move

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5
Q

the cytoskeleton mediates…

A

intracellular transport

(membrane bound vesicles)

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6
Q

the cytoskeleton facilitates…

A

cell division

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7
Q

cytoskeleton components

A
  • actin filaments
  • microtubules
  • intermediate filaments (IF)
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8
Q

cytoskeleton components
- actin filaments

A

Cell movement, provides force
- ~7nm
- Also known as microfilaments
- Two strand polymers of actin protein

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9
Q

cytoskeleton components
- microtubules

A

Cell organization, cell movement, transport network
- ~25nm
- Long tubes made of tubulin proteins

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10
Q

cytoskeleton components
- intermediate filaments

A

Strength, protection
- ~8-12nm
- Thick rope-like fibres made of
heterogenous fibrous proteins

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11
Q

what does the cytoskeleton enable

A

cells to have complex structures

cells to move

cells to be protected from damage

to form an organized function whole cell

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12
Q

ACTIN CYTOSKELETON
what does actin allow?

A

cells to move

how:
disassembly of filaments and rapid diffusion of subunits
reassembly of filaments at a new site
(interaction with other proteins control structure and polymerisation and depolymerisation)

this pushes the membrane in the direction it wants to go
so cell needs to disassemble and assemble actin very quickly

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13
Q

ACTIN CYTOSKELETON
actin monomer

A

G-actin

globular
bound to ATP

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14
Q

ACTIN CYTOSKELETON
actin polymer

A

F-actin

minus end - pointed - shrink

plus end - barbed - growth

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15
Q

ACTIN CYTOSKELETON
is actin abundant?

A

yes
one of the most abundant proteins in our body

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16
Q

ACTIN CYTOSKELETON
staggering

A
  • Going into each other
  • Creates a helical structure
    When in ADP form less stable

When bound to ADP interaction between plus and minus ends are weakened, so they fall off
But new ones are added
* Can regulate this

17
Q

MICROTUBULE CYTOSKELETON
microtubules are made of?

A

alpha-beta-tubulin dimers

18
Q

MICROTUBULE CYTOSKELETON
microtubule structure

A

tubulin heterodimer –> alpha and beta together as building block
(instead of a monomer)

form hollow tubes

Built into a protofilament (single strand of tubulin heterodimers)

These protofilaments are then organised into a microtubule (so lots of protofliaments next to each other kinda making a sheet)

19
Q

MICROTUBULE CYTOSKELETON
Tubulin binds…

A

GTP

  • Both alpha and beta bind to GTP
  • But only the beta subunit can hydrolyse GTP to GDP
20
Q

MICROTUBULE CYTOSKELETON
role of GTP

A

GTP hydrolysis regulates stability of MTs
- GTP –> GDP

Only the beta subunit can hydrolyse GTP to GDP
(very similar to the actin strand)

Conversion of GTP to GDP the microtubules become less stable
Protofilaments become more flexible and the microtubules falls apart
* This is known as shrinking

Ways to stabilise this
GTP gap
- Prevent GTP from being hydrolysed
- This stabilises the whole microtubule

21
Q

MICROTUBULE CYTOSKELETON
intracellular transport

A
  • Motor proteins use the microtubule network to move vesicles and organelles

Different motor proteins travel in different directions by recognising the polarity of microtubules

Plus end is the growing end of the microtubule
Microtubules are the pathways for vesicles

Motor proteins move vesicles

22
Q

MICROTUBULE CYTOSKELETON
SUMMARY
structure

A
  • Microtubules are hollow tubes made up of protofilaments that are formed from a-b tubulin dimers, which are asymmetrical proteins containing GTP
23
Q

MICROTUBULE CYTOSKELETON
SUMMARY
role of GTP

A
  • In b-tubulin within a microtubule, GTP is hydrolysed over time causing the potofilaments to bend and separate, destabilizing the microtubule
24
Q

MICROTUBULE CYTOSKELETON
SUMMARY
dynamic nature enables?

A
  • This polar and dynamic nature of microtubules enables cells to organize their contents in time and space via different motor proteins that track in specific direction along microtubules
25
Q

INTERMEDIATE FILAMENTS
provide…

A

strength and flexibility

26
Q

INTERMEDIATE FILAMENTS
dynamic?

A

much less dynamic

27
Q

INTERMEDIATE FILAMENTS
can form specialist structures?

A

yes

e.g.
Nuclear envelope (lamins)
Keratins
- Hair
- Skin

28
Q

INTERMEDIATE FILAMENTS
assembly and disassembly speed?

A

not as rapid as actin and microtubules

29
Q

INTERMEDIATE FILAMENTS
mutation?

A

Some inherited skin conditions are caused by mutations in intermediate filament genes

e.g. epidermolysis bullosa – mutations in keratin genes

30
Q

INTERMEDIATE FILAMENTS
structure

A
  • Head and tail domain with long helical domain
  • Form dimers which associate with one another in antiparallel fashion

Start with a monomer
The monomer assembles into a dimer and coil together
These dimers associate with each other and go anti parallel

End up with a structure that is really good at resisting force

31
Q

cell division coordinated by…

A

the cytoskeleton

e.g. animal mitosis
nuclear Lamins (Ifs) break down
Microtubules separate chromatids (organisation and transport
Cytokinesis: actin drives cell division (movement of membrane)
Other proteins help (e.g. motor proteins

32
Q

do bacteria have a cytoskeleton?

A

yes

FtsZ – microtubule-like structure

MreB – actin-like structure

Crescentin and others related proteins – intermediate filament-like structure

33
Q

CYTOSKELETON SUMMARY
Actin and microtubules have the same structure in…

A

all eukaryotes

34
Q

CYTOSKELETON SUMMARY
Actin and microtubules perform…

A

similar functions in all eukaryotes

35
Q

CYTOSKELETON SUMMARY
do some eukaryotic groups lack filament fibres?

A

yes

e.g. yeast

36
Q

CYTOSKELETON SUMMARY
prokaryotes have a cytoskeleton made of…

A

proteins structurally related to those in eukaryotes

CELL BIOLOGY AND PHYSIOLOGY (11 decks)

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