cytoskeleton Flashcards
cytoskeleton is made up of what 3 groups of structures
actin filaments (microfilaments)
microtubules
intermediate filaments
cytoskeletal elements subunits are held together by what forces
weak noncovalent forces
role of accessory proteins
-regular length and stability, number and geometry of filaments
-determine site of new filaments
-change kinetics of filaments formation and disassembly
-operate under control extracellular and intracellular signaling
microtubule structure
-alpha, beta tubulin heterodimers that are arranged spirally
-each spiral includes 13 dimers
-longitudinal column called protofilament
where are microtubules located / main functions
cytoplasm, cilia and flagella (cell motility), mitotic spindle (chromosome movement in cell division)
(compression-resisting “griders”), organelle movements
most microtubules grow from where
a region near the nucleus called the microtubule organizing center (MTOC/centrosome)
what tubulin acts as nucleation sites for microtubule growth
gamma
what does colchicine do
antimitotic agent
binds to tubulin, prevents its addition to+ end, depolymerization occurs at - end
kinesis transports organelles along microtubules in what direction
towards the + end (away from MTOC)
dyneins move organelles along microtubules in what direction
towards the - end (towards the MTOC)
centrioles structure and where is it found
-found in centrosomes
-9 triplets of microtubules
-pair of centrioles surrounded by matrix of tubulin subunits
-arranged orthogonally
-replicate before cell division
cilia and flagella structure
-dynein arms, connected to the “A” microubule
-type of ATPase (provides moment)
-axoneme core structure formed of 9 doublets of microtubules w 2 central singlets
-motile, membrane covered processes
basal body
-provides origin to cilium or flagellum
-embedded in the plasma membrane
-similar to a centriole
G-actin vs F-actin
G actin - when monomers are not incorporated into a filament
F-actin - when incorporated into a filament
actin is found where
-muscle fibers
-most cells as part of submembrane network
acting function and mechanism
-contributes to cell shape and locomotion (movement of organelles in the cytoplasm)
-forms stress fibers which allow for cellular crawling
actin filament polymerization and depolymerization and organizing of filaments regulated by what
-actin-binding proteins
-severing proteins
-bundling proteins
-changes in Ca2+
-changes in cAMP
intermediate filament sturcture
-fibrous proteins supercoiled into thicker cables
-more stable and more variable than the other cytoskeletal elements
-formed of coiled-coil dimers which organize themselves into tetramers
keratins is a class of what
intermediate filaments
keratin found in what type of cells and what places
-found in epithelial cells
-abundant in surface layer of epidermis
-form hair, nails, horns, hoofs
vimentin & vimentin like proteins found in tissues derived from what and is a class of what
mesenchyme
intermediate filaments
neurofilaments is a class of what and found only where
class of intermediate filaments
found only in neurons
lamins is a class of what, found where, and function
class of intermediate filaments
found in cell nuclei
form a structural framework for the nucleus
beaded filaments is what specific, and a class of what
class of intermediate filaments
lens-specific
(ex: phakinin, filensin)
what is the protein subunit for intermediate filaments
keratin
intermediate filament function (2)
-anchorage of nucleus and certain other organelles
-formation of nuclear lamina
microfilament (actin structure)
two intertwined strands of actin, each a polymer of actin protein subunits
function of microfilament (5)
-changes in cell shape
-muscle contraction
-cytoplasmic streaming
-cell motility (as in pseudopodia)
-cell division (cleavage furrow formation)
