Kapitel 16

Question 1

Protein complex containing γ-tubulin and other proteins that is an efficient nucleator of microtubules and caps their minus ends.

Answer 1

γ-tubulin ring complex (γ-TuRC)

Question 2

Cell junction in which the cytoplasmic face of the plasma membrane is attached to actin filaments. Examples include adhesion belts linking adjacent epithelial cells and focal contacts on the lower surface of cultured fibroblasts.

Answer 2

adherens junction

Question 3

Complex of proteins that nucleates actin filament growth from the minus end.

Answer 3

ARP (actin-related protein) complex (Arp 2/3 complex)

Question 4

Bundle of microtubules and associated proteins that forms the core of a cilium or a flagellum in eukaryotic cells and is responsible for their movements.

Answer 4

axoneme

Question 5

Membrane protrusion formed when the plasma membrane detaches locally from the underlying actin cortex - allowing cytoplasmic flow and hydrostatic pressure within the cell to push the membrane outward.

Answer 5

blebbing

Question 6

Specialized layer of cytoplasm on the inner face of the plasma membrane. In animal cells it is an actin-rich layer responsible for movements of the cell surface.

Answer 6

cell cortex

Question 7

Short cylindrical array of microtubules - closely similar in structure to a basal body. A pair of centrioles is usually found at the center of a centrosome in animal cells. (Figure 16–48)

Answer 7

centriole

Question 8

Centrally located organelle of animal cells that is the primary microtubule-organizing center (MTOC) and acts as the spindle pole during mitosis. In most animal cells it contains a pair of centrioles. (Figures 16–47 and 17–24)

Answer 8

centrosome

Question 9

Movement of a cell toward or away from some diffusible chemical.

Answer 9

chemotaxis

Question 10

Hairlike extension of a eukaryotic cell containing a core bundle of microtubules. Many cells contain a single nonmotile cilium - while others contain large numbers that perform repeated beating movements. Compare flagellum.

Answer 10

cilium (plural cilia)

Question 11

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 11

cytoskeleton

Question 12

Sudden conversion from growth to shrinkage - and vice versa - in a protein filament such as a microtubule or actin filament. (Panel 16–2 - pp. 902–903)

Answer 12

dynamic instability

Question 13

Large motor protein that undergoes ATP-dependent movement along microtubules.

Answer 13

dynein

Question 14

Thin - spike-like protrusion with an actin filament core - generated on the leading edge of a crawling animal cell. (Figure 16–21)

Answer 14

filopodium (plural filopodia) (microspike)

Question 15

Long - whiplike protrusion whose undulations drive a cell through a fluid medium. Eukaryotic flagella are longer versions of cilia. Bacterial flagella are smaller and completely different in construction and mechanism of action. Compare cilium.

Answer 15

flagellum (plural flagella)

Question 16

Dimeric protein that nucleates the growth of straight - unbranched actin filaments that can be cross-linked by other proteins to form parallel bundles.

Answer 16

formin

Question 17

Actin-rich protrusions extending in three-dimensions that are important for cells to cross tissue barriers by degrading the extracellular matrix.

Answer 17

invadopodia

Question 18

Type of intermediate filament - commonly produced by epithelial cells.

Answer 18

keratin

Question 19

Member of one of the two main classes of motor proteins that use the energy of ATP hydrolysis to move along microtubules. (Figure 16–56)

Answer 19

kinesin

Question 20

Motor protein associated with microtubules that transports cargo within the cell; also called “conventional kinesin.”

Answer 20

kinesin-1

Question 21

Flattened - sheetlike protrusion supported by a meshwork of actin filaments - which is extended at the leading edge of a crawling animal cell. (Figures 16–77 and 16–79)

Answer 21

lamellipodium (plural lamellipodia)

Question 22

Any protein that binds to microtubules and modifies their properties. Many different kinds have been found - including structural proteins - such as MAP2 - and motor proteins - such as dynein. [Not to be confused with the “MAP” (mitogen-activated protein kinase) of “MAP kinase.”]

Answer 22

microtubule-associated protein (MAP)

Question 23

Region in a cell - such as a centrosome or a basal body - from which microtubules grow.

Answer 23

microtubule-organizing center (MTOC)

Question 24

Protein that uses energy derived from nucleoside triphosphate hydrolysis to propel itself along a linear track (protein filament or other polymeric molecule).

Answer 24

motor protein

Question 25

Long - highly organized bundle of actin - myosin - and other proteins in the cytoplasm of muscle cells that contracts by a sliding filament mechanism.

Answer 25

myofibril

Question 26

Type of motor protein that uses the energy of ATP hydrolysis to move along actin filaments.

Answer 26

myosin

Question 27

Type of intermediate filament found in nerve cells. (Figure 16–72)

Answer 27

neurofilament

Question 28

Linear string of microtubule subunits joined end to end; multiple protofilaments associate with one another laterally to construct and provide strength and adaptability to microtubules.

Answer 28

protofilament

Question 29

Structure formed during bacterial cell division by the inward growth of the cell wall and plasma membrane and that divides the cell into two.

Answer 29

septum

Question 30

Cortical fibers of contractile actin-myosin II bundles that connect the cell to the extracellular matrix or adjacent cells through focal adhesions or a circumferential belt and adherens junctions.

Answer 30

stress fibers

Question 31

Process by which a polymeric protein filament is maintained at constant length by addition of protein subunits at one end and loss of subunits at the other. (Panel 16–2 - pp. 902–903)

Answer 31

treadmilling

Question 32

The protein subunit of microtubules. (Panel 16–1 - p. 891 - and Figure 16–42)

Answer 32

tubulin

Question 33

Key target of activated Cdc42. Exists in an inactive folded conformation and an activated open conformation; association with Cdc42 stabilizes the open form - enabling binding to the Arp 2/3 complex and enhancing actin-nucleating activity.

Answer 33

WASp protein