Title: Webstraw: Cell Bio Anki Deck / Section 8 - Cytoskeleton: Microfilaments

Q: [...] make up microfilaments and have [...] function
A: actin; cortical

Q: 3 types of actin-based structures
1. [...] cells - microvilli, cell cortex, adherens belt
2. [...] cells - filopodia, lamellipodium, stress fibers
3. [...] function cells - contractile ring
A: epithelial; migrating; non-muscle

Q: actin are [...] molecules with ATP-binding cleft for at (-) end
A: polar

Q: actin monomers ([...] are made of 4 subunits with ATP-binding cleft
A: G-actin)

Q: [...] are polymers of G-actin formed by ATP hydrolysis
A: F-actin

Q: [...] can be used to decorate actin to show polarity - arrow points to [...] end
A: myosin S1; (-)

Q: actin polymerization occurs at the [...] end
A: (+)

Q: [...] is needed for actin elongation - actin needs to undergo [...] if not present
A: nuclei; nucleation

Q: there are 2 critical concentrations for actin assembly
1. [...] for (+) end - lower Cc and faster rate
2. [...] for (-) - higher Cc and slower rate
A: 0.12um; 0.6um

Q: G-actin needs to be bound to [...] for elongation
A: ATP

Q: [...] occurs when actin concentration is between 2 critical concentrations - monomers move to [...] end
A: treadmilling; (-)

regulation of actin polymerization
1. stockpile of G-actin
2. thymosin - binds to G-actin to prevent polymerization
3. profilin - charges G-ADP to G-ATP to promote polymerization
4. cofilin - promotes depolymerization
5. capping protein CapZ (+) - block assembly and disassembly
6. capping protein tropomodulin (-) - block assembly and disassembly

Q: actin altering drugs
1. [...] - depolymerizes actin
2. [...] - stabilizes actin
A: cytochalasin; phallodin

Q: unbranched microfilament use [...] as nucleating protein at the (+) end and is regulated by [...]
A: formin; Rho-GTP

Q: [...] causes branching in existing microfilaments
A: Arp2/3

Q: Arp2/3 is regulated by nucleation promoting factor (NPF)
1. [...] - activated by GTPase Cdc42
2. [...] - activated by GTPase Rac
A: WASp; WAVE

Q: Arp2/3 can aid in [...] and [...]
A: endocytosis; phagocytosis

Q: [...] is a parasite with rapid Arp2/3 polymerization that shoves actin into adjacent cell
A: listeria

actin-binding proteins
1. fimbrin - bundles actin
2. alpha-actinin - bundles actin
3. filamin - forms actin networks
4. spectrin - forms actin networks
5. dystrophin - supports plasma membrane

Q: actin in red blood cells
1. [...] - anchors spectrin and actin to membrane
2. [...] - forms actin networks
A: ankyrin; spectrin

Q: [...] in microvilli links actin to plasma membrane
A: ezrin

Q: [...] can be found in muscle to link actin to tendons
A: dystrophin

Q: [...] is actin's motor protein
A: myosin

Q: myosin consists of
1. heavy chains - head is [...] and actin binding site, tail binds [...], neck binds light chains
2. light chain - regulates myosin [...]
A: ATPase; cargo; movement

Q: myosin classes
1. Class I: single heavy chain with no tail - membrane [...]
2. Class II: 2 heavy chains - forms [...] filaments for contractions
3. Class V: 2 heavy chains with tail - [...] transport
A: association; thick; organelle

steps in myosin movevment
1. start in rigor state
2. myosin head binds ATP - head released from actin
3. hydrolysis of ATP to ADP + Pi - myosin head goes into cocked state
4. myosin head binds to actin
5. power stroke - powered by release of Pi
6. ADP released and ATP rebinds - myosin head released

Q: [...] are the contractile units of muscles - uses [...] and [...] for contraction
A: sacromeres; ATP; Ca^2^+

Q: components of sacromere
1. [...] - move closer to one another during contraction
2. [...]: thick filaments - does not change in size
3. [...]: place with no thick filament - no change in size
A: Z-disk; A-band; I-band

Q: muscle cells do no want to [...]
A: polymerize/depolymerize

muscle stabilizing proteins
1. capZ - at (+) end
2. tropomodulin - at (-) end
3. nebulin - stabilizes actin
4. titin - holds thick filaments in place
5. dystrophin - links muscle to tendon

Q: [...] stores Ca^2+ used for muscle contraction
A: sarcoplasmic reticulum

Q: sarcroplasmic reticulum is signalled by [...] tubules that travel inside the cell
A: transverse

Q: Ca^2+ binds to [...] to move [...] that is covering mysoin head binding site
A: troponin; tropomyosin

Q: [...] occurs when myosin cannot be released from actin after death and ATP production stops
A: rigor mortis

Q: contractile ring of actin forms around metaphase plate during [...] to separate cells
A: cytokinesis

Q: myosin [...] regulates smooth muscle contraction
A: phosphorylation

Q: myosin need to be [...] for involuntary msucle contraction
A: phosphorylated

Q: [...] contributes to vesicular transport
A: myosin V

Q: [...] in yeast is assisted by actin network transporting cargo
A: budding

Q: cytoplasmic [...] is the moving of the cytoplasm during organelle movement
A: streaming

Q: [...] actin ring forms around moving cytoplasm and helps with streaming using [...]
A: cortical; myosin

Q: cell [...] describes individual cell movement
A: migration

Q: [...] are the actin-myosin contractile units
A: stress fibers

Q: [...] pushes plasma membrane forward - [...] provide traction for movement
A: leading edge; stress fibers

Q: [...] polymerization is active at (+) end and [...] is active at (-) end during cell migration
A: Arp2/3; cofilin

Q: [...] is the signal that attracts a cell to move
A: chemotaxis

Q: steps in cell migration
1. [...] signals activates receptors - causes actin [...] and pushes membrane to the direction of the signal
2. adhesion - new [...] is added
3. translocation - cell body moves forward using action-myosin contraction
4. deadhesion and old adhesion recycling
A: chemotatic; polymerization; focal adhesion

Q: Cdc42, Rac, Rho are proteins that need to be in [...] state for cell migration
A: GTP

Q: 1. active Rho forms [...]
2. active Cdc42 activates [...] to activate Arp2/3
3. Activate Rac activates [...] to make lamellipodia
A: stress fibres; WASp; WAVE

Q: Cdc42 activates [...] - [...] are polymerized to leading edge and transports WASp, WAVE
A: polarity; microtubules

Q: Scratch assay shows that you need all three proteins [...] to activate cell migration
A: Cdc42, Rac, Rho