In developmental biology, what is meant by the concept of "growth"?

a) Growth occurs through increases in cell size.

b) Growth occurs through increases in cell number.

c) Growth can result from increases in the volume of extracellular matrix between cells.

d) Cell death is an important determinant of overall growth.

Which of the following is correct?

#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.

#Question id: 2442

#Unit 2. Cellular Organization

The drug colchicine acts to

a. promote microtubule assembly.     

b. inhibit microtubule assembly.

c. sever microtubules.                        

d. block cell division.

e. cap microtubule ends.

#Question id: 2443

#Unit 2. Cellular Organization

Microtubule-associated proteins

a. typically co-localize with microtubules inside cells.

b. are divided into two types: those that stabilize microtubules and those that destabilize microtubules.

c. typically co-purify with microtubules.                  

d. are similar to α- and β-tubulin.