Chapter 9: The cytoskeleton and cell motility Flashcards
3 elements of the cytoskeleton:
- microtubules
- microfilaments
- intermediate filaments
Roles of the cytoskeleton
- structural support/maintaining cell shape
- internal framework organizing organelles within the cell
- directs cellular locomotion and movement of materials within the cell
T/F: Microtubules are highly branched
FALSE. Microtubules are long, hollow, UNBRANCHED tubes
microtubues are composed of subunits of the protein ____
tubulin
Microfilaments are ccomposed of the protein ____
actin
a MICROTUBULE is a set of GLOBULAR proteins arranged in longitudinal rows called _________
PROTOFILAMENTS
How many protofilaments does a microtubule contain?
13
each PROTOFILAMENT is assembled from dimers of ___ and ____ subunits assembled into tubules with plus and minus ends.
dimers of ALPHA and BETA tubulin subunits
is the core of cilia and flagella is composed of microtubules or microfilaments?
MICROTUBULES
…ya ninny
what does MAPs stand for?
Microtubule-associated proteins
How is the microtubule-binding activity of MAPs controlled?
primarily by the addition and removal of PHOSPHATE GROUPS from particular AMINO ACIDS
T/F: MAPs attach to the surface of microtubules to increase their STABILITY and promote their ASSEMBLY
True.
What is one cause of Alzheimer’s disease related to MAPs?
an abnormally high level of phosphorylation of a certain MAP called “tau.”
The brain cells of people with this disease contain tangled filaments called NEUROFIBRILLARY TANGLES containing excessively phosphorylated tau molecules that are UNABLE TO BIND to MICROTUBULES, contributing to death of nerve cells.
the movement of vesicles and material in the axon is mediated by _________
microtubules
What generate the forces required to move objects within a cell?
motor proteins
T/F: Microtubules have no role in embryogenesis.
False. Microtubules play a role in AXONAL GROWTH during embryogenesis
- movement of material AWAY from the cell body
2. movement of material TOWARDS the cell body
- anterograde
2. retrograde
T/F: molecular motors can move in any direction.
False. Molecular motors move UNIDIRECTIONALLY along the cytoskeletal track in a stepwise manner.
3 classes of molecular motors:
- kinesin
- dynein
- myosin
Along what tracks do kinesin, dynein, and myosin move?
Kinesin and dynein move along MICROTUBULE TRACKS.
Myosin moves along MICROFILAMENT TRACKS.
Motor proteins convert ____ energy into ____energy.
chemical energy (ATP) into mechanical energy.
Which motor protein family moves in an anterograde manner along the microtubule track and which moves in a retrograde manner?
kinesin = anterograde dynein = retrograde
What drives the stepwise movement of motor proteins?
binding and hydrolysis of ATP
What does “KLPs” stand for?
kinesin-like proteins
composition of kinesins
- 2 identical heavy chains
- 2 identical light chains
- each kinesin includes a PAIR OF GLOBULAR HEADS connected to a ROD-LIKE STALK.
T/F: kinesin is a PLUS end-directed microtubular motor based on its movement
true
What is the velocity of the movement of kinesin on a single protofilament of a microtubule proportional to?
ATP concentration
Explain “processive movement”
movement of KINESIN is PROCESSIVE, meaning it moves along an individual microtubule for a long distance without falling off.
KLPs move cargo towards the __________
cell’s PLASMA MEMBRANE
What movement is dynein responsible for?
the movement of CILIA and FLAGELLA
Cytoplasmic dynein is a _____ end directed microtubular motor
minus
Name of adaptor required by cytoplasmic dynein to interact with membrane-bounded cargo:
dynactin
Kinesins move cargo in one direction, towards the ___ end, and the dyneins move it in the opposite direction, towards the ____ end.
Kinesins move cargo in one direction, towards the PLUS end, and the dyneins move it in the opposite direction, towards the NEGATIVE end.
T/F: kinesins and dyneins are ATPases
true
What are MTOCs?
“microtubule-organizing centres”
Specialized structures for the NUCLEATION of MICROTUBULES.
ex. centrosome
What is the centrosome responsible for?
-initiation and organization of the microtubular cytoskeleton
T/F: centrioles are usually found in groups of 4
false. Centrioles are usually found in pairs
Centrosomes contain 2 barrel-shaped _______ surrounded by ________
Centrosomes contain 2barrel-shaped CENTRIOLES surrounded by PERICENTRIOLAR MATERIAL (PCM)
Basal Body
- MTOC
- structure where outer microtubules in a cilia and flagella are generated
Do plants conatin MTOCs? Where are their microtubules organized?
Plants DO NOT contain MTOCs. THeir microtubules are organized around the surface of the nucleus.
What is the name of the protein which is found in MTOCs and is critical for microtubule nucleation?
γ-tubulin
What does γ-TURC stand for?
γ-TUbulin Ring Complex
γ-TURC complex forms a polypeptide scaffold on which ____γ-tubulin molecules are arranged
13
Hydrolysis of what molecule is needed for microtubule assembly?
GTP
Proteins called ____ regulate the rate of growth and shrinkage of microtubules
+TIPS
Axoneme
- central core of cilia and flagella.
- consists of microtubules in a 9 + 2 arrangement
the CENTRAL SHEATH of the axoneme is connected to the a-tubules of peripheral doublets by ____
radial spokes
By what are doublets in an axoneme connected to one another?
by an INTERDOUBLET BRIDGE
What is IFT?
- “intraflagellar transport”
- process responsible for assembling and maintaining flagella
T/F: basal bodies are identical in structure to centrioles
true. basal bodies can turn into centrioles and vise versa
