#Question id: 2436
#Unit 2. Cellular Organization
Cell locomotion
a. requires coordination of motions generated in different regions of the cell.
b. occurs only in cells with a defined polarity.
c. may be controlled by signaling pathways.
d. occurs in a defined sequence of steps.
#Question id: 2437
#Unit 2. Cellular Organization
Membrane extension involves
a. bending actin filaments.
b. myosin II.
c. the Arp2/3 nucleation of new filaments.
d. actin depolymerization.
e. actin polymerization.
#Question id: 2438
#Unit 2. Cellular Organization
Rac, a GTPase superfamily protein,
a. is related to Ras.
b. may be activated by growth factors.
c. stimulates lamellipodia formation.
d. stimulates filopodia formation.
e. stimulates stress fiber assembly.
#Question id: 2439
#Unit 2. Cellular Organization
α- and β-tubulin
a. are highly conserved.
b. bind GTP.
c. hydrolyze GTP to GDP.
d. are found in all eukaryotes.
e. are related to the bacterial protein FtsZ.
#Question id: 2440
#Unit 2. Cellular Organization
Microtubule assembly in vitro requires
a. ATP.
b. a threshold (critical) concentration of tubulin.
c. warming the solution to 37°C.
d. microtubule-associated proteins.
e. GTP.
#Question id: 2441
#Unit 2. Cellular Organization
Which of the following statement(s) is (are) true of microtubule assembly?
a. GDP-tubulin normally assembles into microtubules.
b. Microtubule (-) ends grow faster than microtubule (+) ends.
c. Tubulin subunits assemble to form a protofilament.
d. Microtubules consist of multiple protofilaments.
e. Microtubules with a GTP cap will shorten.