Cytoskeleton Flashcards
What is the cytoskeleton comprised of?
Microtubules, actin and intermediate filaments
Where is the cytoskeleton found?
ALL eukaryotic cells
Describe the cytoskeleton
dynamic, complex, intracellular network of tubules, filaments and fibres
What is the function of the cytoskeleton
give cells shape and function
Where do microtubules start?
single point - microtubule organising centre
What are the roles of microtubules
organisation of cell shape, movement and division
Describe microtubules
hollow tubes of different lengths and sizes
How do microtubules always exist
Dimers together
What is a microtubule (structure)
hetero-polymer of alpha and beta tubulin with a GTP bound molecule
How do the dimers in microtubules arrange themselves
end to end in protofilaments, forming a tube like structure of individual microtubules
TRUE or FALSE - microtubules lack polarity
FALSE
Which end of the microtubule grows slows
minus end
Describe growth at the plus end of the microtubule
fast
What can affect microtubule function
post-translational modifications and microtubule associated proteins
What do microtubules form
mitotic spindle
What acts to create dynamic instability in microtubules?
assembly and the minus and plus ends
What makes up microtubules
tubulin heterodimers
What does the minus end of tubulin become during assembly
mostly GDP
What does the plus end of tubulin become during assembly
mostly GTP
What does tubulin hydrolyse
GTP into GDP
Where does hydrolysis of GTP occur fastest in tubules
Minus end
What is the function of the plus end in microtubules
acts as a cap to protect growing microtubule
What does the assembly of microtubules create
dynamic instabilty
What end of microtubules promotes depolymerisation
plus end
When does microtubule growth stop
when local concentration of GTP tubulin runs out
What is the most stable part of the microtubule
base
What is the microtubule organising centre important for?
polarity and maintaining permanent microtubule network in cell
What is the microtubule organising centre comprised of?
pair of centrioles
What is the function of gamma tubulin in the microtubule organising centre
forms special structure around end of individual microtubules, protects minus end from depolarisation
TRUE or FALSE - ALL microtubules have the same polarity
TRUE
Which end of the microtubule goes out into the cell
plus end
What is a type of microtubule
basal body
What do basal bodies give rise to
spindle poles
What are microtubule associated proteins
proteins that interact with microtubules
What is the function of microtubule associated proteins
regulate turnover of microtubules and promote assembly, stabilise microtubules and maintain function
where is the function of microtubule associated proteins most important
nerve cells
What are the motor proteins (microtubule associated proteins)
dynein and kinesin
Describe Actin microfilaments
fibres of homomeric actin, highly conserved, cell type specific
What is the structure of actin microfilaments
helical geometry, bound ATP
What is the function of bound ATP in actin microfilaments
polymerisation
What are the two forms of actin microfilaments
globular and filamentous
How does actin exist in low concentrations
monomer
What happens at the fast growing end of actin
new ATP actin is added
What modulates actin filament turnover
nucleation factors and actin binding proteins
What is the function of intermediate filaments
provide strength and structural support
Where are intermediate filaments present
most eukaryotic cells EXCEPT fungi
Which type of filament/tubule is the most complex
intermediate filaments
Describe the structure of intermediate filaments
homo or heteropolymeric
where are intermediate filaments found in the cell
cytoplasm
Where can special forms of intermediate filaments be found
nucleus E.G. lamina
What is the function of intermediate filaments in the nucleus
provide structural integrity
What are the five subtypes of intermediate filaments
epithelial keratins, vimentin & desmin, neurofilaments, nuclear lamins
Where do vimentin and desmin exist respectively
vimentin - fibroblasts
desmin - muscle
What regulates the spontaneous self assembly of intermediates filaments
phosphorylation
TRUE or FALSE - intermediate filaments lack polarity
TRUE
Why do intermediate filaments lack polarity
due to anti-parallel strands
