Cytoskeleton Flashcards
what are the sizes of the different cytoskeletal elements
microfilaments 5-9nm
intermediate filaments 10nm
microtubules 25nm
what is the function of the cytoskeleton
support
movement
resist mechanical forces
what is the structure of microfilaments
actin globular
double stranded helix
G actin + ATP makes stable actin oligomers (di/trimers) bonded by covalent bonds
what is the structure of intermediate filaments
alpha helix wound into dimers (rope like)
what is the structure of microtubules
alpha and beta subunits
tubulin globular
hollow tube atttached to centre by centrosome
what is the function of microfilaments
cel shape and mobility
what is the function of intermediate filaments
mechanical support
(less dynamic)
what is the function of microtubules
positioning organelles
transport
what is the critical concentration
Cc = Koff / Kon
conc of free subunits in the cytoplasm
****describe filament polymerisation
actin filaments are dynamic
microfilaments are microtubules have structural polarity due to their shape and orientation
so have a plus end and a minus end
the + end has tubulin bound to a GTP cap which hydrolyses GTP to GDP-tubulin
therefore to prevent the GDP tubulin from being exposed at the + end, more GTP tubulin molecules must join
How does Vincristine act as a chemotherapy drug
binds to tubulin and stops it from polymerising
how does the seal junctions
actin caludins will limit the passage of substances
and maintain polarity
how does the cytokeleton transmit between gap junctions
use connexins to form an electrical or chemical connection between adjacent cell cytoplasms
how does the cytoskeleton achor
junctions together
actin cadherin and catenin hold junctions and desmosomes
actin integrin and actin keratins bind cells to extracellular matrix
(focal adhension + hemidesmosomes)
describe intracellular cell motility
Myosin motor proteins bind to actin (cause muscle contraction)
Kinesin and Dynein bind to microtubules
kinesin moves from - to + end
Dynein moves from + to - end
globular heads use ATP to cause conformational changes in the motor proteins, allowing them to move across the microtubule
