Question

Question 1 of 8 2.0 Points Which of the following statements about the cytoskeleton is false? A. The cytoskeleton is made up of three types of protein filaments. B. The cytoskeleton controls the location of organelles in eukaryotic cells. C. Covalent bonds between protein monomers hold together cytoskeletal filaments. D. The cytoskeleton of a cell can change in response to the environment. Reset Selection

Question 2 of 8 2.0 Points Which of the following statements about the function of the centrosome is false? A. Microtubules emanating from the centrosome have alternating polarity such that some have their plus end attached to the centrosome while others have their minus end attached to the centrosome. B. Centrosomes contain hundreds of copies of the γ-tubulin ring complex important for microtubule nucleation. C. Centrosomes typically contain a pair of centrioles, which is made up of a cylindrical array of short microtubules. D. Centrosomes are the major microtubule-organizing center in animal cells. Reset Selection

Question 3 of 8 2.0 Points The hydrolysis of GTP to GDP carried out by tubulin molecules ________________. A. provides the energy needed for tubulin to polymerize. B. occurs because the pool of free GDP has run out. C. tips the balance in favor of microtubule assembly. D. allows the behavior of microtubules called dynamic instability. Reset Selection

Question 4 of 8 2.0 Points Which of the situations below will enhance microtubule shrinkage? A. addition of a drug that inhibits GTP exchange on free tubulin dimers B. addition of a drug that inhibits hydrolysis of the GTP carried by tubulin dimers C. addition of a drug that increases the affinity of tubulin molecules carrying GDP for other tubulin molecules D. addition of a drug that blocks the ability of a tubulin dimer to bind to γ-tubulin Reset Selection

Question 5 of 8 2.0 Points Which of the following statements is correct? Kinesins and dyneins ____________________. A. have tails that bind to the filaments. B. move along both microtubules and actin filaments. C. often move in opposite directions to each other. D. derive their energy from GTP hydrolysis. Reset Selection

Question 6 of 8 2.0 Points Consider the mechanism by which actin and tubulin polymerize. Which of the items below does not describe something similar about the polymerization mechanisms of actin and microtubules? A. Although both filaments can grow from both ends, the growth rate is faster at the plus ends. B. Depolymerization initiates at the plus ends of filaments. C. Nucleotide hydrolysis promotes depolymerization of filaments. D. Free subunits (actin and tubulin) carry nucleoside triphosphates. Reset Selection

Question 7 of 8 2.0 Points For both actin and microtubule polymerization, nucleotide hydrolysis is important for ______. A. stabilizing the filaments once they are formed. B. increasing the rate at which subunits are added to the filaments. C. promoting nucleation of filaments. D. decreasing the binding strength between subunits on filaments. Reset Selection

Question 8 of 8 2.0 Points Compared to the normal situation, in which actin monomers carry ATP, what do you predict would happen if actin monomers that bind a nonhydrolyzable form of ATP were incorporated into actin filaments? A. Actin filaments would grow longer. B. Actin filaments would grow shorter because depolymerization would be enhanced. C. Actin filaments would grow shorter because new monomers could not be added to the filaments. D. No change, as addition of monomers binding nonhydrolyzable ATP would not affect actin filament length.

Answer 1

1.Correct answer is:C. Covalent bonds between protein monomers hold together cytoskeletal filaments.

2.Correct answer is:A. Microtubules emanating from the centrosome have alternating polarity such that some have their plus end attached to the centrosome while others have their minus end attached to the centrosome.

3.Correct answer is:D. allows the behavior of microtubules called dynamic instability.

4.Correct answer is:A. addition of a drug that inhibits GTP exchange on free tubulin dimers

5.Correct answer is:C. often move in opposite directions to each other.

6.Correct answer is:B. Depolymerization initiates at the plus ends of filaments.

7.Correct answer is:D. decreasing the binding strength between subunits on filaments.

8.Correct answer is:A. Actin filaments would grow longer.