Lecture 15 Flashcards
cytoskeleton
network of protein filaments that make a meshwork in the cytoplasm of eukaryotic cells
dynamic = reshapes itself continuously
role of cytoskeleton
cell support and shape maintenecne
cell divisiion
organelle positioning
organelle and particle movement
cell anchoring
components of cytoskeleton
intermediate filaments
mictotubules
microfilaments
intermediate filaments
rope like
flexible (recoil when stretched)
tough, strong
extend across cytoplasm, go from one jn to another,
give mechanical strength = by cabling
why skin stretches but doesn’t break.
intermediate filaments polymerization, how is it made?
Subunits = fibrous proteins
2 int w ea/o, wrap around together = from dimers
2 dimers come together = from tetramers
When monomers int w eachother N terminals and C ternimals are sperated, each at opp side.
When 2 dimers join together, N of one and C of the second join together.
With this interactions, no polarity, theres no difference in polarity from one side to another
8 tetramers, = int w e/o laterally.= from rope like filament
All int w e/o end by end nad we get a long filamenti
intermediate filament claùsses
- cytoplasmic:
keratin filaments = in epi cells
neurofilaments = in nerve cells
vimentin = in CT tissue muscles, glial cells - nucleir
nuclear laminate = in all animal cells
don’t form bundles but meshwork.
microfilaments
thin, flexible,
mainly in cell cortex(beneath plasma mb
roles of microfilaments
cell shape determining nad maintaining.
movement of whole cell/ part of cell
cell division
muscle contraction
movement of cytosol inside cell
microfilament polymerization
Subunit = actin = globular protien
Monomer create 2 helical polymers, 2 chains of actin proteins int w e/o, grow at the same time and equally
Actin filaments hve polarity = +- end.
Polar bc 2 ends are diff.
actin proteins are added more quickly to + end more than - end.
Is the side that lets the actin filament grows and binds other actin protiens
microfilament depolymerization
the poly. of actin into microfilaments is reversible
At + end, polymerization depends on ATP, actin proteins bind ATP, inc affinity so bind other actin proteins
When hydrolyzzes and lose ATP, and lose affinity so depolarizes.
microfilaments in imp roles int eh cell
allow muscle contraction, slide against myosin proteins during muscle contraction
imp in cell division, create contractile ring during cytokinesis
create microvilli, = cells that line the intestine are folded into tiny projections.
microvilli are supported by microfilaments
allow for cell movement, contract at back to push front
microtubules characteristics
straight cylinders, long, hollow, rigid
found throughout the cytoplasm
microtubules involved in
intracellular trasnport
cell division
organelle positioning
cilia/flagella movement
microtubule polymerization
Globular proteins = tubulin
Alpha and beta = 2 types of monomers
Int w e/o = create a dimer
Dimers polymerize to form a protofilamenet
13x int to form a microtubule (empty tube)
have polarity +- end
Only grow from + end
Bc - end is one attached to centrosomes, so if growing has to happen from +,
dynamic = pol/depol constantly and independently of eachtohers,
grow and shrink w no influence on surr.
microtubules polymerization and depol.
switching back and forth.
Tubulin has GTP = high affinity = binding = growing
Tubulin hydrolyzes GTP = low affinity = no binding. poly
Polymerization is dependent on concentrations of tubulin, if added quickly = before GTP is hydrlzye, will happen
If takes time for next tubulin to be added = wont polymerize but also depol. Will dissociate from eacother.
switching back and forth between poly and deeply is called _____ and leads to _____
dynamic instability and leads to rapid remodelling of microtubule organization
is imp for their fn
microtubules associated with proteins- motor proteins
tubules provide tracks fromovemnt of cytoplasmic material
2 types of motor proteins use microtubules
kinesins(+) and dyneins (-)
motor proteins transport vesicles, macromolecules, and organelles on microtubules.
microtubules in cell division and
make mitotic spindles during cell division and allow chromosomes to segregate
organelles positioning in eukaryotic. cells
kinesis pull ER = towards cytoplasm,
makes sure Golgi is more inwards near the centrosomes,
brings all the vehicles near the centrosome and fuse to make Golgi
cilia and flagella movement
they are moveable appendage on elk cells
cilia move fluids across cell surface (like in GI and resp system)
flagella = propel cells, like sperm cells
inside cilia + flagella= microtubules
