Chapter 17 Key Terms

Question 1

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

Answer 1

Actin-binding protein

Question 2

Thin, flexible protein filament made from 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.

Answer 2

Actin filament

Question 3

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.

Answer 3

Cell cortex

Question 4

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,

Answer 4

Centriole

Question 5

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.

Answer 5

Cilium (plural cilia)

Question 6

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.

Answer 6

Cytoskeleton

Question 7

The rapid switching between growth and shrinkage shown by microtubules.

Answer 7

Dynamic instability

Question 8

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.

Answer 8

Dynein

Question 9

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

Answer 9

Filopodium (plural filopodia)

Question 10

Long, whip-like structure capable of propelling a cell through a fluid medium with its rhythmic beating. Eukaryotic ________ are longer versions of cilia; bacterial _______ are completely different, being smaller and simpler in construction.

Answer 10

Flagella (plural flagellum)

Question 11

Fibrous cytoskeletal element, about 10 nm in diameter, that forms rope-like networks in animal cells; helps cells resist tension applied from outside.

Answer 11

Intermediate filaments

Question 12

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

Answer 12

Keratin filament

Question 13

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

Answer 13

Kinesin

Question 14

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

Answer 14

Lamellipodium (plural lamellipodia)

Question 15

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

Answer 15

Microtubule

Question 16

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

Answer 16

Microtubule-associated protein

Question 17

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

Answer 17

Motor protein

Question 18

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.

Answer 18

Myofibril

Question 19

Type of motor protein that uses ATP to drive movements along actin filaments. One subtype interacts with actin to form the thick contractile bundles of skeletal muscle.

Answer 19

Myosin

Question 20

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

Answer 20

Myosin filament

Question 21

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

Answer 21

Nuclear lamina

Question 22

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).

Answer 22

Polarity

Question 23

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

Answer 23

Rho protein family

Question 24

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

Answer 24

Sarcomere

Question 25

Protein from which microtubules are made.

Answer 25

Tubulin