Chapter 17

Question 1

actin-binding protein

Answer 1

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

Question 2

actin filament

Answer 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.

Question 3

cell cortex

Answer 3

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

Question 4

centriole

Answer 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.

Question 5

centrosome

Answer 5

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.

Question 6

cilium

Answer 6

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.

Question 7

cytoskeleton

Answer 7

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.

Question 8

dynamic instability

Answer 8

The rapid switching between growth and shrinkage shown

by microtubules.

Question 9

dynein

Answer 9

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.

Question 10

flagellum

Answer 10

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

Question 11

intermediate filament

Answer 11

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

Question 12

keratin filament

Answer 12

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

Question 13

kinesin

Answer 13

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

Question 14

microtubule

Answer 14

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

Question 15

microtubule-associated protein

Answer 15

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

Question 16

motor protein

Answer 16

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

Question 17

myofribril

Answer 17

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.

Question 18

myosin

Answer 18

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.

Question 19

myosin-I

Answer 19

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.

Question 20

Myosin-II

Answer 20

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.

Question 21

myosin filament

Answer 21

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

Question 22

nuclear lamina

Answer 22

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

Question 23

polarity

Answer 23

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).

Question 24

sarcomere

Answer 24

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

Question 25

tubulin

Answer 25

Protein from which microtubules are made