cytoskeleton

Question 1

cytoskeleton is made up of what 3 groups of structures

Answer 1

actin filaments (microfilaments)
microtubules
intermediate filaments

Question 2

cytoskeletal elements subunits are held together by what forces

Answer 2

weak noncovalent forces

Question 3

role of accessory proteins

Answer 3

-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

Question 4

microtubule structure

Answer 4

-alpha, beta tubulin heterodimers that are arranged spirally
-each spiral includes 13 dimers
-longitudinal column called protofilament

Question 5

where are microtubules located / main functions

Answer 5

cytoplasm, cilia and flagella (cell motility), mitotic spindle (chromosome movement in cell division)

(compression-resisting “griders”), organelle movements

Question 6

most microtubules grow from where

Answer 6

a region near the nucleus called the microtubule organizing center (MTOC/centrosome)

Question 7

what tubulin acts as nucleation sites for microtubule growth

Answer 7

gamma

Question 8

what does colchicine do

Answer 8

antimitotic agent
binds to tubulin, prevents its addition to+ end, depolymerization occurs at - end

Question 9

kinesis transports organelles along microtubules in what direction

Answer 9

towards the + end (away from MTOC)

Question 10

dyneins move organelles along microtubules in what direction

Answer 10

towards the - end (towards the MTOC)

Question 11

centrioles structure and where is it found

Answer 11

-found in centrosomes
-9 triplets of microtubules
-pair of centrioles surrounded by matrix of tubulin subunits
-arranged orthogonally
-replicate before cell division

Question 12

cilia and flagella structure

Answer 12

-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

Question 13

basal body

Answer 13

-provides origin to cilium or flagellum
-embedded in the plasma membrane
-similar to a centriole

Question 14

G-actin vs F-actin

Answer 14

G actin - when monomers are not incorporated into a filament
F-actin - when incorporated into a filament

Question 15

actin is found where

Answer 15

-muscle fibers
-most cells as part of submembrane network

Question 16

acting function and mechanism

Answer 16

-contributes to cell shape and locomotion (movement of organelles in the cytoplasm)
-forms stress fibers which allow for cellular crawling

Question 17

actin filament polymerization and depolymerization and organizing of filaments regulated by what

Answer 17

-actin-binding proteins
-severing proteins
-bundling proteins
-changes in Ca2+
-changes in cAMP

Question 18

intermediate filament sturcture

Answer 18

-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

Question 19

keratins is a class of what

Answer 19

intermediate filaments

Question 20

keratin found in what type of cells and what places

Answer 20

-found in epithelial cells
-abundant in surface layer of epidermis
-form hair, nails, horns, hoofs

Question 21

vimentin & vimentin like proteins found in tissues derived from what and is a class of what

Answer 21

mesenchyme
intermediate filaments

Question 22

neurofilaments is a class of what and found only where

Answer 22

class of intermediate filaments
found only in neurons

Question 23

lamins is a class of what, found where, and function

Answer 23

class of intermediate filaments
found in cell nuclei
form a structural framework for the nucleus

Question 24

beaded filaments is what specific, and a class of what

Answer 24

class of intermediate filaments
lens-specific
(ex: phakinin, filensin)

Question 25

what is the protein subunit for intermediate filaments

Answer 25

keratin

Question 26

intermediate filament function (2)

Answer 26

-anchorage of nucleus and certain other organelles
-formation of nuclear lamina

Question 27

microfilament (actin structure)

Answer 27

two intertwined strands of actin, each a polymer of actin protein subunits

Question 28

function of microfilament (5)

Answer 28

-changes in cell shape
-muscle contraction
-cytoplasmic streaming
-cell motility (as in pseudopodia)
-cell division (cleavage furrow formation)