Essential Cell Biology: Chapter 17

Cytoskeleton

System of protein filaments in the cytoplasm of a eukaryotic cell that gives the cell shape and the capacity for directed movement. Its most abundant components are actin filaments, microtubules, and intermediate filaments.

Intermediate Filament

Fibrous cytoskeletal element, about 10 nm in diameter, that form ropelike networks in animal cells; help cells resist tension applied from outside.

Actin Filaments

Thin, flexible protein filament made form a chain of globular actin molecules; a major constituent of all eukaryotic cells, this cytoskeletal element is essential for cell movement and for the contraction of muscle cells.

Tubulin

Protein from which microtubules are made.

Myosin Filament

Polymer composed of interacting molecules of myosin-II; interaction with actin promotes contraction in muscle and nonmusical cells.

Desmosome

Specialized cell-cell junction, usually formed between two epithelial cells, that serves to connect the ropelike keratin filaments of the adjoining cells, providing tensile strength.

Nuclear Lamina

Fibrous layer on the inner surface of the inner nuclear membrane formed as a network of intermediate filaments made form nuclear lamins.

Keratin Filament

Class of intermediate filament abundant in epithelial cells, where is provides tensile strength; main structural component of hair, feathers, and claws.

Vimentin Filaments

Neurofilaments

Nuclear Lamins

Epidermal Bullosa Simplex

Progeria

Centrosome

Microtubule-organizing center that sits near the nucleus in an animal cell; during the cell cycle, this structure duplicates to form the two poles of the mitotic spindle.

Mitotic Spindle

Array of microtubules and associated molecules that forms between the opposite poles of a eukaryotic cell during mitosis and pulls duplicated chromosome sets apart.

Cilium

Hairlike structure made of microtubules found on the surface of many eukaryotic cells; when present in large numbers, its rhythmic beating can drive the movement of fluid over the cell surface, as in the epithelium of the lungs.

Flagellum

Long, whiplike structure capable of propelling a cell through a fluid medium with its rhythmic beating.

Motor Protein

Protein such that a myosin or kinesin that uses energy derived from ATP hydrolysis to propel itself along protein filament or polymeric molecule.

Microtubule

Long, stiff, cylindrical structure composed of the protein tubulin. Used by eukaryotic cells to organize their cytoplasm and guide the intracellular transport of macromolecules and organelles.

Polarity

An inherent asymmetry that allows one end of an object to be distinguished from another; can refer to a molecule, a polymer (such as an actin filament), or even a cell (for example, an epithelial cell that lines the mammalian small intestine).

Plus end/Minus end

Centriole

Cylindrical array of microtubules usually found in pairs at the center of a centrosome in animal cells. Also found at the base of cilia and flagella, where they are called basal bodies.

Nucleation Site

Dynamic Instability

The rapid switching between growth and shrinkage shown by microtubules.

Colchicine/Taxol

Microtubule-Associated Protein

Accessory protein that binds to microtubules; can stabilize microtubule filaments, link them to other cell structures, or transfer various components along their length.

Kinesin

A large family of motor proteins that uses the energy of ATP hydrolysis to move toward the plus end of a microtubule.

Dynein

Motor protein that uses the energy of ATP hydrolysis to move toward the minus end of a microtubule. One form of the protein is responsible for the bending of cilia.

Ciliary Dynein

Primary Cilium

Actin

Actin-Binding Proteins

Protein that interacts with actin monomers of filaments to control the assembly, structure, and behavior of actin filaments and networks.

Microvilli

Contractile Bundles

Contractile Ring

Structure made of actin and myosin filaments that forms a belt around a dividing cell, pinching it in two.

Treadmilling

Cell Cortex

Specialized layer of cytoplasm on the inner face of the plasma membrane. In animal cells, it is rich in the actin filaments that govern cell shape and drive cell movement.

Neutrophils

Lamellipodium

Dynamic sheetlike extension on the surface of an animal cell, especially one migrating over a surface.

Filopodium

Long, thin, actin-containing extension on the surface of an animal cell. Sometimes has an exploratory function, as in a growth cone.

Formins

Myosin-I

Simplest type of myosin, present in all cells; consists of a single actin-binding head and a tail that can attach to other molecules or organelles.

Rho Protein Family/Rac/Cdc42

Family of small, monomeric GTPases that controls the organization of the actin cytoskeleton.

Skeletal Muscle

Cardiac Muscle

Smooth Muscle

Myosin-II

Type of myosin that exists as a dimer with two actin-binding heads and a coiled-coil tail; can associate to form long myosin filaments.

Myofibril

Long, cylindrical structure that constitutes the contractile element of a muscle cell; constructed of arrays of highly organized bundles of actin, myosin, and other accessory proteins.

Sarcomere

Highly organized assembly of actin and myosin filaments that serves as the contractile unit of a myofibril in a muscle cell.

Transverse Tubules

Sarcoplasmic Reticulum

Tropomyosin/Troponin

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basal lamina

extracellular matrix

hemidesmosome