Cytoskeleton: Microtubules, Microfilaments, and Intermediate Filaments

Comprehensive vocabulary flashcards covering the structure, protein components, diameters, locations, and functions of microtubules, microfilaments, and intermediate filaments.

Cytoskeleton

A complex network of microtubules, microfilaments, and intermediate filaments, along with proteins that link them to each other and to the cell membrane to form a framework called the microtrabecular lattice.

Microtrabecular Lattice

The structural framework inside a cell formed by microtubules, microfilaments, and intermediate filaments linked together and to the cell membrane by proteins.

Microtubules (MT)

Hollow cylinders of fixed diameter ($24\,\text{nm}$ to $25\,\text{nm}$) with a wall made of 13 parallel protofilaments formed by $\alpha$ and $\beta$ tubulin subunits.

Microtubular Organizing Center (MTOC)

A cellular structure containing gamma tubulin rings that directs the assembly, elongation, and shortening of microtubules from polymerized tubulin molecules.

Gamma Tubulin

A type of tubulin found in rings within the microtubular organizing center (MTOC) that directs the polymerization of microtubules.

Functions of Microtubules

Determining cell shape and elongation, intracellular transport of organelles, vesicles, and macromolecules, forming the mitotic spindle during cell division, and forming centrioles, cilia, and flagella.

Cancer Chemotherapy (Microtubule Inhibition)

Therapy used to arrest cell proliferation in tumors by preventing microtubule formation.

Microfilaments

Fine protein strands measuring $5-7\,\text{nm}$ in diameter, composed of two chains of globular G actin coiled around each other to form filamentous F actin.

G-actin

Globular actin protein subunits that polymerize into two coiled chains to form filamentous F actin.

F-actin

Filamentous actin formed by two chains of globular G actin coiled around each other.

Functions of Microfilaments

Facilitating cell shape changes (endocytosis, exocytosis, amoeboid pseudopod movements), intracellular transport of organelles and granules, cell cleavage during division, muscle contraction, and forming the core of microvilli.

Intermediate Filaments

Supportive cytoskeletal fibers measuring $8-10\,\text{nm}$ in diameter formed by the polymerization of chemically differing tetrameric subunits.

Cytokeratin

A specific intermediate filament protein present in the cells of epithelial tissue.

Vimentin

An intermediate filament protein located in cells of connective tissue and muscular tissue.

Desmin

An intermediate filament protein found specifically in the cells of muscular tissue.

Neurofilaments

Intermediate filament proteins located in the neurons of nervous tissue.

Glial Fibrillar Acidic Protein (GFAP)

An intermediate filament protein found in the glial cells of nervous tissue.

Lamins

Intermediate filament proteins located in the nuclear envelope.

Immunocytochemical Identification of Intermediate Filaments

A diagnostic method used to identify the intermediate filament proteins of a tumor to determine its specific cell of origin for diagnosis and treatment.

Immunofluorescent Technique

A light microscopy technique required to visualize cytoskeletal elements (microtubules, microfilaments, and intermediate filaments) that are otherwise difficult to see.