cytoskeleton Flashcards
cytoskeleton
protein filaments in eukaryotic cells
primary filament systems comprising the cytoskeleton
microtubules
microfilaments (actin filaments)
intermediate filaments
cytoskeletal works to
create internal architecture to give the cell its shape
accessory proteins link cytoskeleton to one another the plasmalemma and or membranes of intracellular organelles
function of cytoskeleton (filaments and tubules)
structural support
intracellular movement and transport
cell locomotion
chromosome seperation
muscle contraction (specialized cells)
3 major cytoskeleton filaments are
actin filaments (microfilaments)
microtubules
intermediate filaments
Actin (microfilaments)
thin filament 6-8nm in diameter
distributed in 3D network throughout cytoplasm
important in maintaining cell shape
facilitate cell changes during movement
ex. wound contration during healing
what forms actin filaments
smaller g-actin subunits
g-actin = small globular protein monomer that polmerizes to form protofilaments
2 protofilaments twist together to form a double helix = F-actin
these combine to make larger actin filaments
terminal web
a support meshwork formed by actin and filamin
prevents cells from deformation
microvilli and stereocilia
increase surface area of cell
core of actin filaments that anchor to the terminal web of the cell
Myosin
thick filament - 15 nm
motor protein
long rod shaped with globular heads
myosin heads form cross bridges between adjacent filaments
Intermediate Filaments
8-10 nm or 10-15 nm (how it is on the slides)
primarily structural
heterogenous group / makeup varies between cells
generally form large filaments that bind with intracellular structures
useful in tumor id
cytokeratin
characteristic of all epithelial cells
forms tonofibrils in epidermis of skin
Intermediate filaments
vimentin
intermediate filament found in mesodermal cells of mesenchymal origin
included endothelial cells muscle and neuroectodermal cells
desmin
intermediate filament unique to muscle cells
mesodermal origin
neurofilament proteins
present in nerve cells
GFAP (glial fibrillary acidic protein)
found in glial support cells of nervous system
astrocytes
Lamin
forms layer on inside of nuclear membrane
Epidermolysis bullosa simplex disorder
giant blisters caused by mechanical stress
disrupts binding of basal epidermal cells - no attachment -> cannot resist friction
mutation in intermediate filament genes cytokeratins 5 &15
cytokeratins role in disease diagnosis
primary intermediate filaments
can stain for a variety of cytokeratins that can be used to confirm if a tumor is of epithelial origin or is a carcinoma
Immmunohistochemistry staining
can be use to confirm tissue type
desmin/muscle
neurofilaments/nervous
microtubules
24nm
composed of 2 types of globular protein -> alpha and beta tubulin
arranged in coiled spiral pattern and polymerize to form hollow tubes
involved in cell movement maintenance of cell shape and intracellular transport
microtubules and intracellular movement
movement occurs through the addition or subtraction of tublin subunits from microtubules
capping proteins stabilizes the growing end of the tubules
motor proteins (dynein and kinesin) attach to microtubules to organelles
Kinesin
moves things away from cell body
dynein
takes things back toward cell body
Microtubules are found in
cilia and flagella
centrioles (used for cell division)
basal bodies of cilia
mitotic spindles
Axoneme
9 pairs of microtubules -> peripheral doublets contain dynein arms arragned in a circle with a central doublet
radial spokes
in an axoneme it connects the central double to the peripheral doublets
nexin
in axoneme connects peripheral doublets to each other
Centrioles
located in the centrosome near the nucleus
function in cell division
each centrioles consists of 9 triplets of microtubules arranged in a cylinder
nucleation center for microtubules
