Lecture 18 - The Cytoskeleton & CM: Muscles Flashcards
def: responsible for the movement of biomolecules and other cellular components over long distances
microtubules
at the ends of MT, cargo switch over to __________ for local movements
microfilaments
what are the functions of a myosin motor protein?
- muscle contraction
- cell movement
- phagocytosis
- vesicle transport
most myosin motors move toward the (+) end, but _______ is an exception
myosin VI
what does the globular head of myosin bind?
actin and uses ATP hydrolysis to move along the filament
myosin move along ____
MF
which can take bigger steps, kinesin or myosin V?
- myosin = 36 nm
- kinesin = 8nm
def: can form bipolar filaments, are important for muscle contraction, cytokinesis, cell migration, and focal adhesions, with 2 heavy chains
Type II myosins
myofibrils are subdivided along their length into repeating units called __________
sarcomere
sarcomeres are comprised of :
- thick, myosin II - bipolar filaments
- thin, actin microfilaments
def: staggered arrays if myosin II
thick filaments
def: actin microfilaments with other bound proteins
thin filaments
def: long, rod-like molecule that fits in grooves along the sides of the F-actin helix
tropomyosin
def: comprised of three polypeptides: TnT, TnC, and TnI
troponin
what is the ratio of troponin and tropomyosin associating with each other?
1:1
def: caps the (-) ends of the filaments to maintain stability
tropomodulin
def: caps the (+) ends and attaches the microfilament to the Z line
CapZ
def: stabilizes and bins the thin filament to the Z line
nebulin
def: cross-links the Z line to the microfilament, keeping the thin filaments in parallel arrays
alpha-actinin
def: bundles the myosin molecules
myomesin
def: attaches the thick filaments to the Z lines and keeps thick filaments correct position relative to think filaments during contraction
titin
how are cross bridges formed ?
by interactions between the actin-binding domains of myosins in the thick filament and the F-actin of the thin filaments
what is opened when muscle cells receive nerve impulses at the neuromuscular junction?
ryanodine receptor, which triggers release of Ca2+ into sarcoplasmic reticulum
when does muscle contraction stoP?
when Ca2+ is actively transported back into the sarcoplasmic reticulum
what does calcium binding to TnC do?
changes the conformation of troponin, pulling tropomyosin off the myosin binding site
def: thin sheet of cytoplasm
lamellipodium
def: thin pointed protrusion
filopodium
what happens in lamellipodia?
loose networks of actin form a dendritic network pushing on the membrane
def: complex of actin-related proteins that nucleate new branches on the sides of filaments
Arp2/3 complex
def: directional movement in response to a graded chemical stimulus
chemotaxis
def: occurs through the formation of protrusions predominantly on one side of a cell
directional migration
def: cells move toward a higher concentration of the diffusible molecules
chemoattractants
def: cells move toward a lower concentration of the diffusible molecules
chemorepellents
