1
Q
- Which of the following classes of microtubules is attached to chromosomes?
a. Kinetochore microtubules
b. Astral microtubules
c. Polar microtubules
d. Interphase microtubules
A
a. Kinetochore microtubules
2
Q
- Whether a microtubule shrinks or grows is determined by
a. The presence or absence of -tubulin
b. The phosphorylation state of -tubulin
c. The rate of GTP-bound tubulin addition relative to the rate of tubulin GTP hydrolysis
d. The rate of ATP hydrolysis relative to the rate of ATP-bound tubulin addition
A
c. The rate of GTP-bound tubulin addition relative to the rate of tubulin GTP hydrolysis
3
Q
- Which of the following statements about cilia is false?
a. They are about 10 micrometers in length and cells that have them usually have many of them
b. They are projections of the plasma membrane supported by microfilaments
c. They can be used to move fluids over the cell surface or to move the cell through fluids
d. Their movement relies upon the motor activity of axonemal dynein.
A
a. They are about 10 micrometers in length and cells that have them usually have many of them
4
Q
- Actin-binding proteins have all of the following functions except
a. Filament severing/depolymerization
b. Microfilament incorporation into the extracellular matrix
c. End capping
d. Filament initiation and polymerization
A
b. Microfilament incorporation into the extracellular matrix
5
Q
- Which of the following statements is true about intermediate filaments?
a. They are involved in cell movement.
b. Rather than consisting of a single type of protein, they can be made up of a number of different proteins
c. The basic structure of an intermediate filament protein is a globular head and a long -helical tail
d. Like microfilaments, they exhibit treadmilling
A
b. Rather than consisting of a single type of protein, they can be made up of a number of different proteins
6
Q
- The approximate diameter of an actin filament is
a. 25 nm
b. 5 mm
c. 7 nm
d. 8-12 nm
A
c. 7 nm
7
Q
- Myosin 2 is found in skeletal muscle and the contractile ring. It is a two-headed myosin with tails that can form thick filaments. Other myosins such as myosin 1 or myosin 5 do not form thick filaments and yet are still capable of producing movement along actin filaments. To what do the tail(s) of myosin 1 or myosin 5 bind?
a. Cargo such as membrane vesicles or intermediate filaments
b. Centrosomes
c. Chromosomes
d. Tubulin
A
a. Cargo such as membrane vesicles or intermediate filaments
8
Q
- Both colchicine and colcemid
a. Block microtubule organizing centers
b. Block microtubule disassembly by binding to microtubule ends
c. Block microtubule assembly by binding to free tubulin
d. Accelerate microtubule disassembly by binding to tubulin in microtubules, causing those molecules to exit the microtubule more quickly
A
c. Block microtubule assembly by binding to free tubulin
9
Q
- Keratin filaments are anchored to junctions called
a. Adherens junctions
b. Tight junctions
c. Desmosomes
d. Gap junctions
A
c. Desmosomes
10
Q
- The discovery that the intermediate filament protein keratin is essential for mechanical strength of epithelial cell layers was made in
a. Small invertebrates
b. Transgenic mice
c. Cell cultures
d. Organ cultures
A
b. Transgenic mice
11
Q
- Which of the following is true about myosin 1?
a. It is involved in muscle contraction
b. It links the actin bundles to the plasma membrane in the microvilli of intestinal cells
c. It does not act as a molecular motor
d. It has a long -helical tail through which it forms homodimers
A
b. It links the actin bundles to the plasma membrane in the microvilli of intestinal cells
12
Q
- The association between actin filaments and the plasma membrane is mediated by all of the following except
a. Catenin links to cadherins
b. Myosin 1-calmodulin linkages
c. Talin links to integrins
d. Direct interaction between actin and plasma membrane proteins
A
d. Direct interaction between actin and plasma membrane proteins
13
Q
- ADF/cofilin plays a role in
a. The nucleation of microfilaments
b. The disassembly of microtubules
c. The disassembly of microfilaments
d. Stimulation of actin filament formation
A
c. The disassembly of microfilaments
14
Q
- Actin filaments are bound into bundles of parallel filaments by the proteins
a. Filamin and spectrin
b. Troponin and tropomyosin
c. Profiln and thymosin
d. alpha actin and fimbrin
A
d. alpha actin and fimbrin
15
Q
- Integrins bind to
a. Collagen
b. Fibronectin
c. Laminin
d. All of the above
e. None of the above
A
d. All of the above
16
Q
- A centrosome is
a. a chromosomal region that connects sister chromatids during mitosis and attached them to the spindle
b. a cylindrical structure made up of nine triplets of microtubules
c. a protein structure that binds centromeres and mediates the attachment of chromosomes to the spindle
d. the major microtubule-organizing center in animal cells
A
d. the major microtubule-organizing center in animal cells
17
Q
- which of the following is not true of the assembly of actin filaments?
a. Polymerization occurs from both the plus and minus ends
b. It begins with the formation of an aggregate of three actin monomers
c. It requires ATP
d. Polymerization is faster from the plus end than from the minus end
A
c. It requires ATP
18
Q
- In red blood cells, which of the following cytosolic proteins is the link between the plasma membrane and the spectrin/actin network beneath the cell surface?
a. Ankyrin
b. Glycophorin
c. Dystrophind
d. Band 3
A
a. Ankyrin
19
Q
- Like myosins, kinesins and dyneins are both families of proteins. Which of the following statements is true of all kinesins and dyneins?
a. The motor activity of the proteins resides in their light chains
b. They are plus-end-directed mtoros
c. They are microtubule-dependent motors
d. They are minus-end-directed motors
A
c. They are microtubule-dependent motors
20
Q
- Which of the following is not one of the functions of the cytoskeleton
a. Cell locomotion
b. To provide a structural framework for the cell
c. Protein translocation into the ER
d. Intracellular movement of organelles and other structures
A
c. Protein translocation into the ER
21
Q
- Actin may be cross-linked into either parallel or ___ bundles
a. Contractile
b. Networks of actin filament
c. Orthogonal filament
d. Antiparallel
A
a. Contractile
22
Q
- Kinesin and dynein are
a. Intermediate filament proteins
b. Microtubule motor proteins
c. Microfilament motor proteins
d. Proteins within centrosomes that mediate nucleation of microtubules
A
b. Microtubule motor proteins
23
Q
- In cell movement, branched actin filament growth pushes against the cell membrane. Proteins involved in this process include all of the following except
a. Profiling
b. WASP/Scar
c. Vinculin
d. Arp2/3
A
c. Vinculin
24
Q
- The basis for muscle contraction is
a. Expansion of the sarcomere
b. Rotation of myosin fibers around actin fibers
c. The sliding of myosin and actin fibers past one another
d. Movement of the Z discs away from one another
A
c. The sliding of myosin and actin fibers past one another
25
25. The major cation responsible for regulating actin-myosin contraction is
a. H+
b. Na+
c. Ca2+
d. K+
c. Ca2+
26
26. Branching of actin filaments can be initated by
a. Arp2/3
b. Formin
c. ADF/cofilin
d. Fimbrin
a. Arp2/3
27
27. Myosin ____ is present in muscle sarcomeres
a. I
b. II
c. III
d. IV
b. II
Molec Cell
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