Lecture 17 - Cytoskeleton & CM: Motor Proteins Flashcards
def: movement of a cell or organism through the environment, movement of the environment past or through the cell, movement of components in the cell
cell motility
def: the shortening of muscle cells, and is a specialized form of motility
cell contractility
what are the 2 eukaryotic motility systems?
- interactions between microtubules and motor proteins kinesics and dyenins
- interactions between actin microfilaments and members of the myosin motor proteins
motor proteins convert chemical energy into __________ _________
mechanical energy
how to molecular motors move?
unidirectionally along their cytoskeletal components in a step wise manner
what are the 3 categories of molecular motors?
- kinesins
- dyneins
- myosins
what do each of the molecular motors use as tracks?
kinesis and dyneins use microtubules and myosin use microfilaments
T or F: motors undergo cycles of ATP hydrolysis, release of ADP + Pi, and acquisition of a new ADP molecule
true
do motor proteins have momentum?
no, they are subject to tremendous friction
are motors processive?
yes they move along a cytoskeletal filament for significant distances
traffic toward the (-) ends of microtubules is considered _____________; toward the (+) end is _______________-
inbound and outbound
def: movement of vesicles and organelles along microtubules
fast axonemal transport
____________ is involved in ATP-dependent transport toward the plus ends (away from the centrosome), called ____________ ________ ____________
Kinesin I, anterograde axonal transport
___________ ______________ moves particles in the opposite direction towards the minus end, called __________ ___________ _____________
retrograde axonal transport
what is the size of steps that kinesis move along the microtubules in
8 nm
what are the 4 parts of a Kinesin I tetramer?
- a globular head region that attaches to MTs (act as ATP hydrolyzing engine)
- a neck region (connect head to stalk)
- a coiled helical stalk region (provide flexibility)
- a light chain region (attaches kinesis to proteins, organelles, or other cargo)
KRP tail regions are ________ ___________-
highly divergent, reflecting cargo diversity
def: moves with HIGH processivity toward the minus ends of microtubules
cytoplasmic dyneins
does dynein directly interact with cargo?
no it requires an adaptor molecule like dynactin and spectrin
def: generate motility in the cilia and flagella
axonemal dyneins
T or F: organelles may bind kinesin and dynein simultaneously with motors engaging in a tug of war type battle for the cargo
true
def: found in unicellular and multicellular eukaryotes, display an oar-like pattern of beating, generating a force perpendicular to the cilium
cilia
_________ cilia move fluid through tracts
motile
____ ______ ______ cilia are thought to have sensory functions
non-motile
def: move cells through a fluid environment, they are the same diameter as cilia, but usually longer
flagella
force generated by flagella is ________ to the flagellum
parallel
what is the common structure shared between cilia and flagella
axoneme
where do cilium/flagellum emerge from?
basal body and surrounded by an extension of the cell membrane
between the axoneme and basal body is a __________ ________ in which the microtubules begin to take on the pattern characteristic of the axoneme
transition zone
the axoneme consists of _______ ________ ________ _________ surrounding a ________ _______ _________ __________
nine peripheral microtubule doublets, central pair of single microtubules
each microtubule double consists of ?
- 1 complete microtubule
- 1 incomplete microtubule
the central tubules are enclosed by a _________ connected to the peripheral doublets by radial spokes
sheath
__________ ____________ project from the A microtubule as pairs of “arms”
axonemal dyneins
what does the assembly and disassembly of cilium and flagellum require?
the transport of material to and form the distal tip
def: movement of structural components between the peripheral doublets and the cell membrane
intraflagellar transport
def: pulls the IFT trains towards the cilium/flagellum tip
Kinesin-2
def: causes microtubule sliding within the axoneme allowing cilia and flagella to bend, there is no change in the overall length of the microtubules
axonemal dynein
the stem of each axonemal dynein molecule is tightly anchored to the outer surface of the __ __________
A tubule
def: the presence of this prevents the sliding of the doublets past each other
nexin
at any given time, what is the status of the axonemal dyneins on either side of the axoneme
one side is active while the other is not
where are primary cilia used?
in sensory structures
