If the intracellular [Ca2+] is 10⁻⁷ mol/L and the extracellular [Ca2+] is 2 × 10⁻³ mol/L, at what potential difference across the cell membrane will Ca2+ be at electrochemical equilibrium?

#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.

#Question id: 2444

#Unit 2. Cellular Organization

Kinesin I moves vesicles