The Cytoskeleton

Flashcards about the Cytoskeleton, Cell Motility, Microtubules, Centrosomes, Centrioles, Cilia, Flagella, Microfilaments, Intermediate Filaments

What is the Cytoskeleton?

A network of fibers extending throughout the cytoplasm that provides mechanical strength, establishes cell shape, enables locomotion, and facilitates intracellular transport.

What are the three main types of fibers in the cytoskeleton?

Microtubules, microfilaments (actin filaments), and intermediate filaments.

What is the main function of microtubules?

Determine the positions of membrane-enclosed organelles and are involved in intracellular transport.

What is the main function of microfilaments?

Determine the shape of the cell and are necessary for whole-cell locomotion.

What is the main function of intermediate filaments?

Provide mechanical strength and resistance to shear stress.

What are microtubules?

Hollow tubes composed of 13 columns of tubulin molecules; function in cell shape maintenance, motility, chromosome movement, and organelle movement.

What are microfilaments (actin filaments)?

Two intertwined strands of actin; function in cell shape maintenance, changes in cell shape, muscle contraction, cytoplasmic streaming, cell motility, and cell division.

What are intermediate filaments?

Fibrous proteins supercoiled into thicker cables; function in cell shape maintenance, anchorage of nucleus and organelles, and formation of the nuclear lamina.

What does cell motility require?

Interaction of the cytoskeleton with motor molecules in an ATP-dependent manner.

What are the two major groups of microtubule motors (kinesins and dyneins)?

Kinesins move toward the plus end, while dyneins move toward the minus end.

What are the functions of microtubules?

Shape and support the cell, resist compression, serve as tracks for organelle movement, separate chromosomes during cell division, and are components of centrosomes, centrioles, cilia, and flagella.

What is a centrosome (microtubule-organizing center)?

A region near the nucleus from which microtubules sprout; it contains a pair of centrioles in animal cells.

What are centrioles?

They are composed of nine sets of triplet microtubules arranged in a ring and are found in animal cells.

What are cilia and flagella?

Constructed from microtubules and provide locomotion for the cell or move fluid past the cell.

How do a flagellum and cilia generate force?

A flagellum has an undulating motion to generate force in the same direction as the flagellum’s axis; cilia work like oars, generating force perpendicular to the cilium’s axis.

What ultrastructure do cilia and flagella have?

Microtubules core sheathed in an extension of the plasma membrane, a "9+2" arrangement of microtubules, and anchored in the cell by a basal body.

What is a microfilament (actin filament)?

A twisted double chain of actin subunits that bears tension.

What are microvilli?

Bundles of microfilaments make up the core of microvilli to increase cell surface area for transport.

What is cytoplasmic streaming a result of?

Actin-myosin interactions and sol-gel transformations.

What are muscle fibers composed of and how do they contract?

Made of actin filaments arranged parallel to one another, with myosin interdigitated with actin; contraction results from the sliding of actin and myosin.

What are intermediate filaments?

Cytoplasmic ropelike fibers that provide a supporting framework, with keratins, nuclear lamins and neurofilaments being examples.

What do intermediate filaments do to nerve cells?

Strengthen the long extension (axon) of nerve cells that transmit impulses.