chapter 13 Flashcards
(42 cards)
The ________ is a complex network of interconnected filaments and tubules that extends
throughout the cytosol from the nucleus to the inner surface of the plasma membrane.
A) cytoskeleton
B) microtubule apparatus
C) axoneme
D) desmin sheath
E) microfilament array
A
Cytoskeletal elements are found in
A) bacteria.
B) archaea.
C) eukaryotes.
D) B and C only.
E) A, B, and C.
E
Which of the following is not a function of the cytoskeleton?
A) Cell locomotion
B) Cell division
C) Organelle movement
D) Establishing cell shape
E) Passive transport
E
Which of the following cytoskeletal proteins is found in prokaryotes?
A) Keratin
B) Tubulin
C) Crescentin
D) Vimentin
E) Actin
C
Microfilaments function in
A) muscle contraction.
B) cytoplasmic streaming.
C) cell division.
D) maintenance of animal cell shape.
E) All of the above.
E
Microtubules have an outer diameter of
A) 7 nm.
B) 8—12 nm.
C) 25 nm.
D) 7 mm.
E) 25 mm.
C
Microtubules contribute to each of the following except
A) intracellular transport.
B) the human red blood cell disklike shape.
C) orientation of plant cellulose microfibrils.
D) filopodial structure.
E) mitotic spindles.
D
Intermediate filaments
A) are 7 nm in diameter.
B) can be composed of the protein vimentin.
C) are abundant in plant cells.
D) are the only cytoskeletal filament responsible for animal cell shape.
E) A, B, C, and D.
B
Which technique would best be used to visualize movement of unlabeled vesicles along
microtubules?
A) Immunofluorescence microscopy of fixed material
B) Live cell fluorescence microscopy
C) Computer-enhanced digital video microscopy
D) Deep-etch electron microscopy
E) A, B, C, or D would be equally useful.
C
Which of the following is true about the structure of the microtubule wall?
A) α-β-tubulin heterodimers are arranged with mixed orientation in each protofilament, and
protofilaments are arranged with mixed polarity in the microtubule wall.
B) α-β-tubulin heterodimers are arranged with the same orientation in each protofilament, and
protofilaments are arranged with mixed polarity in the microtubule wall.
C) α-β-tubulin heterodimers are arranged with the mixed orientation in each protofilament, and
protofilaments are arranged with same polarity in the microtubule wall.
D) α-β-tubulin heterodimers are arranged with the same orientation in each protofilament, and
protofilaments are arranged with same polarity in the microtubule wall.
E) Orientation of the α-β-tubulin heterodimers is completely random and depends on which end
of the dimer first hits the end of the microtubule when it assembles.
D
Which phase of microtubule polymerization in vitro would be affected most by adding short
microtubules to unpolymerized GTP-tubulin?
A) Lag phase
B) Elongation phase
C) Addition of tubulin dimers to microtubule (+) ends at the plateau phase
D) Addition of tubulin dimers to microtubule (−) ends at the plateau phase
E) Treadmilling
A
Which of the following is false about dynamic instability of a microtubule end?
A) During a growth phase, assembly of GTP-tubulin is faster than incorporated GTP is
hydrolyzed, forming a GTP-cap.
B) During a catastrophe phase, hydrolysis of incorporated GTP is faster than GTP-tubulin
addition, forming a GDP-cap.
C) During rescue, GTP-tubulin assembles fast enough to reestablish a GTP cap.
D) Each end of a microtubule can undergo dynamic instability independently.
E) A, B, C, and D are true.
E
Tubulin may assemble onto one end while disassembling from the other end of the same
microtubule simultaneously in a process known as
A) dynamic instability.
B) treadmilling.
C) nucleation.
D) oligomerization.
E) catastrophe-rescue.
B
The critical concentration for tubulin polymerization is the concentration of
A) tubulin dimers at which all dimers assemble into microtubules.
B) unassembled tubulin dimers when assembly is balanced with disassembly.
C) tubulin dimers at which dimers assemble onto microtubule minus ends but disassemble from
plus ends.
D) unassembled tubulin dimers when there is net disassembly of dimers from both microtubule
ends.
E) tubulin dimers in most cells.
B
Dynamic assembly and disassembly of a cytoplasmic microtubule in a cell occurs primarily
at its plus end, because its minus end is usually anchored to
A) a basal body.
B) a centromere.
C) a microtubule organizing center.
D) a mitochondrial outer membrane.
E) the plasma membrane.
C
Axonemal microtubules are
A) dynamically unstable.
B) anchored on basal bodies.
C) randomly oriented in the axoneme.
D) required to maintain axons.
E) involved in intracellular organelle transport.
B
________ causes microtubules to form tight bundles in nerve cell axons.
A) MAP2
B) EB1
C) Tau
D) FtsZ
E) Desmin
C
Which of the following proteins is associated with the precise control of where microtubules
depolymerize during mitosis?
A) Tau
B) Stathmin/Op18
C) Gelsolin
D) Catastrophins
E) MAP 2
D
CapZ
A) causes microfilaments to lengthen by assembly at their plus ends.
B) depolymerizes microfilaments at their plus ends.
C) prevents assembly and disassembly at microfilament plus ends.
D) forms microfilament branches.
E) connects microfilaments to microtubules.
C
Intermediate filaments
A) lack the intrinsic polarity of microtubules and microfilaments, because IF tetrameric subunits
are symmetric.
B) are grouped into six classes.
C) are the most stable and least soluble cytoskeleton filaments.
D) are not found in plant cell cytoplasm.
E) All of the above are true.
E
Centrosome ring-shaped complexes contain ________ and ________.
A) α-tubulin; β-tubulin
B) γ-tubulin; MCAK
C) γ -tubulin; MAP2
D) γ-tubulin; GRiPs
E) γ-tubulin; crescentin
D
What is the effect of cofilin on an actin microfilament?
A) Caps the microfilament plus end
B) Caps the microfilament minus end
C) Increases turnover of ATP-actin at the microfilament plus end
D) Increases turnover of ADP-actin at the microfilament plus end
E) Increases turnover of ADP-actin at the microfilament minus end
E
A microtubule-organizing center (MTOC)
A) contains centrioles in plant cells.
B) serves as a site for both microtubule and intermediate filament assembly.
C) anchors either end of cytoplasmic microtubules.
D) anchors only the minus ends of cytoplasmic microtubules.
E) usually is positioned near the cell membrane.
D
________ is a drug that blocks cell division by stabilizing microtubules; as a result, it is used
in the treatment of ________.
A) Vincristine; listeriosis
B) Vinblastine; lung cancer
C) Taxol; breast cancer
D) Nocodazole; athlete’s foot
E) Colchicine; gout
C
