Test 3: Cytoskeleton Flashcards
Cytoskeletons allow cells to…
organize itself and interact with environment mechanically
3 classes of cytoskeletons are… they…
- intermediate filmanets -> mechanical strength and cell integrity against sheer stress
- microtubules -> positions cell components & transports, basis of cilia and flagella
- actin filaments -> cell shape and motility
Actin filmanets have formation between subunits that is…
weak; noncovalent
Intermediate Filament: Provides mechanical strength by…
- forming network thru cell
2. anchors at PM/ECM
Intermediate Filament: 4 major classes. where are they?
- keratin -> epithelia
- vimentin -> connective, muscle, glial
- neurofilemin -> nerve
- nuclear lamin -> nucleus
Intermediate Filament: are stabilized by x, which…
accessory proteins; connect intermediate filmanet to other cytoskeleton such as actin filmanet or microtubules
Intermediate Filament: arrange in 2 shapes, they are
cross link and bundle
Tubulin and Actin: Both have polarity. + end for (fast/slow) growing called (NTP/NDP), and - end for (fast/slow) growing called (NTP/NDP)
+: fast; NTP
-: slow, NDP
Tubulin and Actin: Tubulin’s Nucleotide is x; Actin’s nucleotide is y.
Tubulin: G
Actin: A
Dynamic Instability is
rapid change in growth and disassembly due to difference between NTP and NDP bound form; ratio of NDP and NTP determinesgrowth or disassembly
Polymerization Time Corse is sigmoidal graph. 3 phases are…
- Nucleation (log phase)
- elongation (growth phase)
- steady state (equilibrium)
Microtubule: Unlike actin monomers, tubulin has…
dimers (α or β)
Microtubule: Order from smallest to largest from dimers to microtubule; rigid/flexible?
dimers (α or β) –> protofilmanet (13) –> microtubule; rigid
Actin: Order from smallest to largest from monomer to flmaent; rigid/flexible?
monomer -> 7 protofilament -> filament; flexible
Growth: 1. Nucleation: for both actin and microtubule, based on…
2 subunits binding and remaining bound (stable enough for 3rd to bind)
Growth: 1. Nucleation: Microtubule: nucleated by… from…
nucleated by γ-tubulin, from Microtubule Organizing Center (MTOC; centrosome in animal, spindle pole body in microorganism); MTOC only source of microtubulins
Growth: 1. Nucleation: Actin: nucleated by…
nucleated by preexisting actin filament via protein Arp 2/3 complex, which binds to preexisting actin filament to nucleate it at 70’
Growth: 2. Elongation: Also called
Dynamic Instability
Growth: 2. Elongation: for both actin and microtubule, growth is due to presence of…
NTP-bound form, which stabilizes the filments
Growth: 2. Elongation: for both actin and microtubule, NTP is constantly hyrdrolyzed into NDP. Hence, + rate means
shrinking
Growth: 2. Steady State: for both actin and microtubule,
when growth = shrink
Actin Filament cross-links in 2 different shapes with 2 different…
rigidity
T/F Severing of filmanet change cell shape and rigidity
T
Motor Proteins: binds to … and uses …
bind to filaments and move along them using ATP hydrolysis
