Lodish Ch 18: Cell Biology - Microtubules and Filaments

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Questions and Answers

A microtubule protofilament is formed by the:

lateral association of only 9-tubulin subunits.

head-to-tail association of tubulin dimers. (correct)

head-to-tail association of only 9-tubulin subunits.

lateral association of tubulin dimers.

In cells, the 9-tubulin ring complex is found:

along the outer wall of the microtubule.

at the microtubule (+) end.

in the hollow core of the microtubule.

at the microtubule (-) end. (correct)

The alpha and beta tubulin proteins can bind:

to ATP or ADP.

to GTP or GDP.

only to GDP.

none of the above (correct)

Where are microtubules observed to be present in different polarities?

dendrites of nerve cells Signup and view all the answers

At MTOCs, microtubule nucleation is facilitated by:

g-tubulin. Signup and view all the answers

Growing microtubule ends are normally stabilized by:

a GTP cap. Signup and view all the answers

The drug taxol acts to:

stabilize microtubules against depolymerization. Signup and view all the answers

A drug that prevents microtubules from depolymerizing could be used to:

inhibit mitosis Signup and view all the answers

Microtubule assembly requires:

a tubulin concentration in excess of the C Signup and view all the answers

MAP2 and Tau are examples of microtubule:

stabilizing proteins Signup and view all the answers

The EB1 protein has several functions. Which of the following is/are true regarding EB1?

all of the above Signup and view all the answers

Which of the following is NOT a way in which a microtubule switches from growing to shortening?

treatment with colchicine Signup and view all the answers

The region of a motor protein that interacts with the motor's cellular cargo is the:

tail domain Signup and view all the answers

All of the following statements describe kinesin-I EXCEPT:

kinesin-I is a (-) end-directed motor. Signup and view all the answers

The ______ serves as a template for the unusual structure of axoneme microtubules.

basal body Signup and view all the answers

For kinesin motors, the direction of movement along a microtubule is specified by the motor's:

neck region Signup and view all the answers

Which of the following is true regarding the transport of cargo by cytoplasmic dynein?

LIS1 associates with the head region of dynein to facilitate transport Signup and view all the answers

The force for axoneme bending is derived from the:

sliding movement of outer doublet microtubules. Signup and view all the answers

The primary cilium:

is nonmotile because it lacks the "central pair" of microtubules. Signup and view all the answers

Which of the following is NOT true about cilia?

All cells with cilia are motile because of the axonemal dynein motor. Signup and view all the answers

Separation of spindle poles during spindle formation and anaphase B most likely depends on which of the following?

(+) end-directed microtubule motors in the microtubule overlap zone Signup and view all the answers

Which of the following occurs during anaphase A?

Kinetochores remain attached to shortening kinetochore microtubules. Signup and view all the answers

In the mitotic spindle, astral microtubules function to:

anchor the spindle poles to the plasma membrane. Signup and view all the answers

Treadmilling through kinetochore microtubules can be observed by:

fluorescence speckle microscopy Signup and view all the answers

Kinetochores assemble at the:

centromere Signup and view all the answers

Capture of microtubule (+) ends by chromosomes occurs during:

prometaphase Signup and view all the answers

Poleward movement of chromosomes during anaphase A requires:

kinetochore motor proteins Signup and view all the answers

Which of the following does NOT belong to the intermediate filament protein family?

laminin Signup and view all the answers

The important role that intermediate filaments play in the epithelial cells of the skin is evident in which of the following?

Patients with mutations in keratin genes exhibit skin problems. Signup and view all the answers

Which of the following is true about intermediate filaments?

Staggered, antiparallel tetramers give intermediate filaments strength. Signup and view all the answers

Study Notes

Microtubules and Intermediate Filaments

Microtubule protofilaments are formed by the head-to-tail association of tubulin dimers.
The 9-tubulin ring complex is located at the microtubule's minus (-) end.
Most microtubules originate in the microtubule-organizing center (MTOC).
Microtubule protofilaments are head-to-tail assemblies of tubulin dimers, with 13 composing the microtubule wall.
Alpha and beta tubulin subunits bind GTP or GDP, but not to ATP or ADP.
Tubulin subunits are normally stabilized by a GTP cap.
The drug taxol stabilizes microtubules against depolymerization.
Loss of a GTP cap causes a microtubule to switch from growth to shortening.
Colchicine blocks microtubule assembly.
Microtubule assembly requires ATP.

Microtubule Nucleation

Microtubule nucleation is facilitated by g-tubulin at the microtubule-organizing centers (MTOCs).
Growing microtubules are typically stabilized by a GTP cap.
Microtubules can originate from centrioles or basal bodies, which are usually part of the MTOC.

Motor Proteins

Motor proteins like kinesin and dynein use ATP hydrolysis to move along microtubules.
Kinesin typically moves toward the plus (+) end of a microtubule.
Dynein typically moves towards the minus (-) end of a microtubule.
Dynactin links dynein to microtubules.
Neuronal vesicles may contain both kinesin and dynein for bidirectional transport along microtubules.

Intermediate Filaments

Intermediate filaments are a type of cytoskeletal protein.
Keratin, vimentin, and desmin are examples of intermediate filament proteins.
Laminin is NOT an intermediate filament protein.
Intermediate filaments are important for mechanical strength of cells, especially in epithelial cells.
Intermediate filaments are stable and don't typically exhibit dynamic instability.
During mitosis, intermediate filaments are disassembled and then reassembled.

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Description

Test your knowledge about microtubules and intermediate filaments, including their structure, formation, and function within the cell. This quiz covers topics such as tubulin dynamics, microtubule nucleation, and the effects of drugs on microtubule stability.