Cytoskeleton Flashcards
cytoskeleton definition
building blocks of cell structure
what does cytoskeleton include
skeleton and muscles of cells
functions of cytoskeleton
architecture, shape, motility of cells and organelles
3 main components of cytoskeleton
microtubules, microfilaments, intermediate filaments
what is the composition of microtubules
tubulin dimers with alpha and beta tubulin
what is tubulin
a GTPase
accessory proteins associated with microtubules
microtubule- associated proteins (MAPs)
function of MAPs
stabilization of polymers, regulate interactions between cytoskeleton elements,
organize MTs
properties of microtubules
DYNAMIC, can go rapid bouts of assembly/disassembly, acts as substrate for motor proteins to transport cargo
function of microtubules
-make up mitotic spindle
-railways for organelle transport
-cell shape
-in neurons for axonal transport
-backbone for cilia and flagella
microtubules are ______ with a ____ end and a ______ end
polarized, plus, minus
the plus end of microtubules is ______, the minus end is _______
dynamic, static
how many protofilaments in a microtubule
13 +/-
the + end has ______ of tubulin addition and removal, the - end has _____ of addition and removal
faster, slower
catastrophe
periods of growth switched to shrinkage (drastic drop in graph)
rescue
switched from shrinkage to growth (drastic increase on graph)
microtubules are ______ near the nucleus, _______ away from the nucleus
negatively charged, postively charged
which motor proteins are associated with microtubules and which end do they move towards
dynein (moved towards - end), kinesin (moves towards + end)
nucleation definition
genesis of a cytoskeletal polymer
where does nucleation occur
at the centrosome
polymerization definition
elongation of a cytoskeletal polymer after initial nucleation
which tubulin is needed for nucleation
gamma tubulin
how do microtubules function in cell division
segregate chromosomes, reorganize cytoplasm
where is cilia found in the body
lung epithelium, trachea, fallopian tube
what is the function of cilia
to move phlegm
basal body definition
microtubule organizing center for cilia and flagella, has a +/- end
axoneme definition
9+2 microtubule structure of cilia and flagella (9 doublets surrounding 2 in the middle)
immotile cilia syndrome
defect in axonemal structure, results in lung disease and sterile males (microtubule malfunction)
Kartagener’s syndrome
situs inversus (reverse body asymmetry) and immotile cilia syndrome
Cancer
disruption of Microtubule dynamics to block cell division (Taxol)
Lissencephaly
mutations in microtubule proteins LIS1 and doublecortin
Charcot-Marie-Tooth disease Type 2A
mutation in specific kinesin/ mutation in mitofusion2
Neurodegenerative disorders
mutations in tau, dyein, kinesin, spastin
neurotropic viruses
can exploit neuron’s microtubule based transport system to reach cell bodies
microfilaments composition
helical, non-hollow, polymers of actin
what is actin
an ATPase
difference between microtubules and microfilaments
microfilaments don’t have organizing centers like centrosome for microtubules,
microfilaments can be nucleated anywhere in the cell
structure of microfilaments
polarized filament with barbed and pointed end
which end of the microfilament favors assembly (polymerization)
barbed end
functions of microfilaments
cleavage furrow (finals stages of mitosis), cell motility, short-range organelle transport, contractility
3 actin isoforms and location
-alpha actin: muscle specific
-beta actin: most cells
-gamma actin: most cells
what must actin be loaded with for nucleation and polymerization
ATP loaded
Stress Fibers
myosin, alpha actin, formins
leading edge meshworks
Arp 2/3, profilin, cofilin
myosin definition
F-actin associated force generating mechanoenzymes
myosin function
contractility, intracellular transport
which side do myosins move to
barbed end of filaments
cytokinesis definition
F-actin and myosin II at contractile ring during cell division
microvilli
actin based epithelial projections
where are microvilli found in the body
small intestine, ear cells
microvilli function
to increase the SA of cells to increase absorption
erythrocyte cytoskeleton
spectrin tetramer, actin, adducin, tropomyosin
Hereditary Spherocytosis
deforms red blood cells to fragile spherocytes b/c of weak binding affinity of spectrin to band 4.1 (malfunction of actin)
Hereditary elliptocytosis
deforms red blood cells to ellipocytes because of incomplete formation of spectrin (actin malfunction)
Breast Cancer
tensin (actin protein) is disrupted which promotes metastatic migration of cancer cells (tensin links integrin receptors to actin)
Familial hypertrophic cardiomyopathy
mutations in cardiac actin
symptoms include, dizziness, chest pain, symptoms of heart failure
Mutations in skeletal muscle actin
congential myopathies, structural abnormalities of muscle, variable degrees of muscle weakness
mutation in Myosin VI
causes deafness ( stereocilia)
mutation in myosin VII
deafness, neurological disorder, blindness (Usher syndrome Type 1)
Phalloidin
found in death cap mushroom, very toxic, binds tightly to and stabilizes actin, preventing depolymerization
intermediate filaments structure
non-polarized, NON-dynamic, less conserved than microtubules or microfilaments
intermediate filaments function
-space filling elements
-gives tensile strength
-specialized functions depending on the cell
-important at cell junctions
Type I and II: intermediate filaments
acid, neutral/basic keratins
epithelial cells and derivatives
Type III intermediate filaments
vimentin, desmin, glial fibrilary acidic protien
fibroblasts, muscle cells, glial cells
Type IV intermediate filaments
NF-L/M/H
Neurons
Type V intermediate filaments
nuclear lamins A, B , C
nuclear lamina of nucleated cells
Epidermolysis bullosa simplex
mutation in keratin expressed in basal cell layer,
results in very sensitive skin to mechanical injury
Progeria
fast aging disease, mutation in nuclear lamina protein
