Cytoskeleton and Cell Motility

Flashcards reviewing the structure, function, and components of the cytoskeleton, including microtubules, motor proteins (kinesins and dyneins), and microtubule-organizing centers (MTOCs).

What are the three filamentous structures that compose the cytoskeleton?

Microtubules, actin filaments, and intermediate filaments

What are the functions of the cytoskeleton?

-Provides structural support and maintains cell shape,

-positions organelles,

-directs movement of materials,

-generates forces for locomotion,

-and is essential for cell division

Name four locations where microtubules are found.

The cytoskeleton, the mitotic spindle, centrioles, and the core of cilia and flagella

What are protofilaments?

Longitudinal rows assembled from dimeric building blocks of α-tubulin and β-tubulin subunits.

Which end of a microtubule is terminated by a row of β-tubulin subunits?

The plus end

Which end of a microtubule is terminated by a row of α-tubulin subunits?

The minus end

What are MAPs?

Microtubule-associated proteins that increase stability and promote microtubule assembly.

How do microtubules provide mechanical support?

By resisting forces that might compress or bend the fiber.

What can defects in transport along microtubules result in?

Neurological diseases like Lou Gehrig’s disease (ALS)

What are the two superfamilies of motor proteins that move along microtubules?

Kinesin and Dyneins

What provides the energy necessary to fuel the motor’s activity?

ATP binding and ATP hydrolysis

What serves as the force-generating engines in Kinesins?

Globular heads

What is the mechanism used by Kinesins?

“Hand-over-hand” mechanism

Kinesin moves toward which end of the microtubule?

Plus end

Cytoplasmic dynein moves toward which end of the microtubule?

Minus end

Name three functions of cytoplasmic dynein.

-Positions the spindle and moves chromosomes during mitosis,

-positions the centrosome and Golgi complex,

-and moves organelles, vesicles, and particles through the cytoplasm

What do MTOC's control?

-Number of microtubules,

-Polarity of microtubules,

-Number of protofilaments,

-Time and location of assembly

Where does microtubule nucleation take place?

Inside a cell, where it occurs in association with a variety of specialized structures called microtubule- organizing centers (or MTOCs).

What is the best studied MTOC in animals?

The centrosome

What is the function of basal bodies?

Forms at the base of the cilium or flagellum.

What are the three types of cytoskeletal filaments?

Microfilaments, intermediate filaments, and microtubules.

What are microfilaments primarily composed of?

Actin protein subunits.

What role do intermediate filaments play in cells?

They provide structural support and help maintain cell shape.

What is the composition of microtubules?

Tubulin protein subunits.

How are cytoskeletal filaments held together?

By weak, noncovalent bonds

What are microtubules?

hollow, relatively rigid, tubular structures made up of a protein called tubulin.