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SGU: Cytoskeleton

Histology: Cytoskeleton

QuestionAnswer
What are the three major components of the cytoskeleton? actin filaments (microfilaments), intermediate filaments and microtubules
What is the function of the cytoskeleton? maintains cell shape and support, provides the mechanisms for cell movement, acts as tracks for motor proteins that help move materials within cells
Describe actin filaments F-actin that is ATP dependent. 7nm. Polarized:fast growing + and slow growing -
Functions of microfilaments anchorage, structural core of microvilli, locomotion, extension of cell processes
Describe microvilli cyclindrical, membrane-bound cytoplasmic projections of a core 25-30 actin microfilaments. The actin is crosslinked by villin anchored to the terminal web.
Describe Intermediate filaments 8-12nm, rope-like, formed from non-polar and variable subunits
Functions of intermediate filaments stabilize cell structure: maintain nuc and organelle position, resist shearing force:connects with desmosomes and hemidesmosomes across the cytoplasm, essential for integrity of cell-cell and cell-ECM junctions
What are the 4 intermediate filaments? keratins, vimentin & vimentin-like, neurofilaments, lamins
Describe keratins diverse group with >50 isoforms, found in different cells of epithelial origin
Describe vimentin most abundant in mesoderm-derived cells
Describe vimentin-like desmin in muscle cells, glial fibrillary protein in glial cells and astrocytes, peripherin in neurons
Describe neurofilaments formed from a group of neurofilament triplet proteins, extend from cell body into the ends of axons and dendrites, provide structural support
Describe lamins associated with nuc envelope, Lamin A & B, found in nucleoplasm
Describe the stucture of a centriole 9 triplets of microtubules arranged around a central axis. Each triplet consists of 1 complete and 2 incomplete microtubules fused
Function of centriole organizes the centrosome, provide basal bodies necessary for assembly of cilia and flagella, formation of centrosome & alignment of the mitotic spindle during cell division
What is the structure of the centrosome/MTOC? pair of centrioles perpendicular to each other with an amorphous protein matrix and gamma-tubulin ring complexes where microtubules grow from
Function of MTOC? initiate microtubule formation: positive ends point out and grow toward the cell periphery
Structure of microtubules? non-branching, rigid, hollow tubes made up of alpha and beta tubulin subunits with a positive and negative end
Which cytoskeletal component is "dynamic"? microtubules because the assemble and disassemble as the needs of the cell change
Functions of microtubules intracellular transport, cell motility, mitotic spindle, rigid intracellular skeleton to main cell shape and polarity
Describe the polymerization of microtubules directed by MTOCs, dependent on GTP, can be highly dynamic or relatively stable, fast grow at positive end and slow growth/disassembly at negative end
controller of microtubule lenght environment and microtubule associated proteins
Function of cilia move fluid and particles along epithelial surfaces
How are cilia anchored to the cell? basal body
What are primary cilia? antennae-like structures, 9+0, develops from one centriole following division
What sensory organelles are derived from primary cilia? outer segment of rods, chemoreceptors in olfactory neurons, mechanoreceptors on epithelial cells of kidney to monitor fluid flow.
What defect arises from polycystic kidney disease? primary cilia defect
What is part of the actin based molecular motor family? myosin
What is part of the microtuble based molecular motor family? kinesin, dynein
Structure of myosin II? 2 heavy chains and 4 light chains, tail-tail interactions result in the formation of bipolar thick filaments, head binds and hydrolyzes ATP
Describe the kinesin family of molecular motors positive end directed motors, binding sits for vesicles, organells or other microtubule, ~40 kinesins in humans
Describe the dynein family negative end directed motors, binding sites for vesicles, organelles and another microtubule, largest and fastest
What are the two branches of dynein cytoplasmic and axonemal
What are the 3 steps of cell motility? protrusion, attachement, contraction
Describe protrusion actin-rich structures pushed out at the front of the cell
Describe attachment actin cytoskeleton connects across PM to substratum
Describe contraction bulk of the trailing cell cytoplasm in drawn forward
What are the 3 different types of protusion filopodia, lamellipodia, pseudopodia
Describe filopodia 1 dimen., core o long, bundled actin filaments ex. fibroblasts
Describe lamellipodia and examples 2 dimens. sheet like structures, ex. fibroblasts, epithelial cells, neurons
Describe pseudopodia 3 dimensional projections, ex. neutrophils
Desribe in detail PM protrusion actin polymerization: actin filaments oriented with plus end forward and minus end attached to sides of other actin by ARP complexes, treadmilling: assemble at front, disassembling at rear
What proteins are involved in cell motility? monomeric GTPases, Rho, Rac, Cdc24
Function of Rho bundling of actin filaments with myosin II, clustering of integrins to form focal contacts
Function of Rac actin polymerization at periphery
Function of Cdc24 actin polymerization and bundling to form filopodia/microspikes
What are the three methods of neutrophil migration neutrophil extravasation, transmigration, chemotaxis
Describe neutrophil extravasation movement from blood to tissues through blood vessels. EC selectin receptors bind neutrophils
Describe transmigration diapedesis: extension of a pseudopod between endothelial cells.
Created by: mnoronha