cytoskeleton Flashcards
what are 3 functions of the cytoskeleton in cells
division of chromosomes in mitosis- cytokinesis
drives organelle movemetn
support for plasma membrane
describe 5 commonalities of actin, microtubules and intermediate filaments
made from repetitive subunits for flexibility
helical arrangement
held together by non covalent links
different properties due to different structures
interconnected system of bundled fibres and lattices
where do actin, microtubules and intermediate filaments extend from
nucleus to plasma membrane
what are microtubules
polarised structures made of tubulin dimers
long straight and rigid. hollow
what tubulin genes are in microtubules
six a, seven b and also y
describe the dimer arrangement in microtubules
head to tail; polarised + and - ends
what does MTOC stand for
microtubule organising centre
describe the 5 stages of MT growth as part of the centrosome
located next to nucleus
plus end grow out of this
duplicates in interphase- each half a duplicated centriole pair
centrosomes move to opposite sides of the nucleus
during mitosis form the mitotic spindle
what is dynamic instability in MTs
some MTs stop growing suddenly and shrink back rapidly
what are the two MT forms and what caises them
t form- GTP bound
d form- GDP bound- less strong
what does MAPs stand for
microtubule associated protein
what are the two types of MAPs
stabilisers/structural and motors
what are three types of MAP motors
mysoin
kinesin
dyein
what do MAP motor proteins do
bind to polarised filaments (actin and microtubules) using ATP hydrolysis
how are the different MAP motor proteins differentiated (3)
cargo they move
direction of movement
filaments they bind to
what is the direction of kinesin and dyein
to plus end
to minus end
what are 4 things that kinesin consists of
two helical heavy chains that dimerise to form a stalk
two light chains which are flexible
a tail that interacts with cargo
two globular ends that interact with microtuble and ATP
describe two features of dyein
forms a large macromolecular assembly
are used for the beating of cilia and flagella
what are cilia and flagella made of and what do they consist of
microtubules and dyeins and bundles of microtubules
what are axonemes
conserved in evolution
9 special doublet microtubules one complete and one half- fused
describe the movement of axoneme
action same for cilia or flagella
requires ATP
sliding of microtubules prevented by protein links
therefore movement causes bending
what is actin
helical plymers of monomers of glubular actin
what are three things G-actin can exist as
atp-actin adp-pi-actin or gdp-actin
how is an actin protofilament formed
from a linear chain of subunits
how do protofilaments form actin
two protofilaments of actin subunits then twist arounf each other to form actin filament
what are the two end types filaments have
pointed and barbed
slow dissociated and get addition of monomers
what happens as actin ages
atp-actin hydrolyses to adp-pi-actin anf then phosphate released to form adp-actin
what are three forms of f-actin
meshwork
tight parallel bundle
contractile bundle
are there more proteins for microtubules or actin
actin
name three species in which you get intermediate filaments
vertebrates, nematodes, molluscs
what is the structure of intermediate filaments
elongated molecules with a central helical domain that forms a coil-coil with another molecule in same direction - pair then form a rope like structure
