Deck 35: Molecular Motors

Question 1

A helical

Answer 1

lever arm

Question 2

Which of the following is a prokaryotic protein similar to tubulin?

A) troponin
B) tubulin
C) axoneme
D) flagellin
E) FtsZ

Answer 2

E

Question 3

Which of the following is common to myosins, kinesins, and dyneins?

A) P-loop NTPase
B) S1 fragment
C) EF-hand domain
D) hexameric AAA ATPase
E) None of the answers is correct.

Answer 3

A

Question 4

What is the functional unit of a muscle cell?

A) myosin
B) actin
C) mitochondria
D) sarcomere
E) None of the answers is correct.

Question 5

Which of the following is a bundle of nine microtubule pairs surrounding two singlet microtubules?

A) axoneme
B) dynein
C) Arp-actin
D) tropomyosin
E) None of the answers is correct.

Question 6

A molecule such as glucose that attracts bacteria is known as a _____.

A) chemorepellant
B) chemostimulant
C) chemoattractant
D) chemotactic
E) chemostatic

Question 7

Bacterial flagella rotate in one direction for smooth swimming and in the other direction to cause _______________.

Question 8

During a muscle contraction, the thin filaments (actin, tropomyosin, troponin) slide along the _________________.

Question 9

Troponin reacts in response to the _______________ ion.

Question 10

Which of the following is a proteolytic fragment of muscle myosin?

A) heavy chain
B) S1
C) P-loop NTPase
D) EF-hand domain
E) $\alpha$ -meromyosin

Question 11

Myosin light chains are related to the _______________ family of proteins.

Question 12

What are flagella used for in bacteria?

A) chemostasis
B) chemoselection
C) chemokinesis
D) chemotaxis
E) chemoprotection

Question 13

Taxol inhibits the proliferation of cells by stabilizing the polymer form of _________________.

Question 14

What is the name given to actin monomers?

A) B-actin
B) D-actin
C) G-actin
D) M-actin
E) S-actin

Question 15

The change in position along a microtubule by the two kinesin monomers is transmitted through a __________________.

Question 16

What part of kinesin undergoes conformational change after nucleotide binding?

A) head domain
B) light chain
C) $\alpha$ -helical lever arm
D) switch II
E) neck linker

Question 17

Microtubules are tracks for kinesins and _________________.

Question 18

Single molecules of myosin in action were studied using __________________.

Question 19

Which of the following was the first kinesin to be discovered?

A) microtubule-linked kinesin
B) conventional kinesin
C) actin-coupled kinesin
D) $\alpha$ -kinesin
E) AAA kinesin

Question 20

Bacterial flagella are polymers composed of 53-kd subunits of a protein called _______________.

Question 21

The structure in a bacterial flagellar motor that rotates is referred to as

A) the MS ring.
B) flagellin.
C) CheY.
D) C-ring
E) None of the answers is correct.

Question 22

The structure of dynein lends itself to the formation of

A) monomeric proteins.
B) dimers.
C) oligomers.
D) dynein fibers.
E) None of the answers is correct.

Question 23

Binding of ATP causes ______________.

A) a decrease in myosin head affinity for actin filaments
B) an increase in myosin head affinity for actin filaments
C) no change in myosin head affinity for actin filaments
D) cross-linking of the myosin head and actin filaments
E) complete abolition of affinity between actin and myosin

Question 24

Regulated actin polymerization is central to the changes in

A) shape of macrophages.
B) cell motility in amebae.
C) flagella movement in bacteria.
D) shape of macrophages and cell motility in amebae.
E) All the answers are correct.

Question 25

How do molecular motors work?

Question 26

Actin polymers will assemble

A) automatically by self-assembly.
B) only in the presence of myosin.
C) with the aid of chaperone proteins.
D) in the presence of GTP
E) None of the answers is correct.

Question 27

What is the rate and distance of the movement of myosin heads?

A) Each head moves 5 times per second, approximately 110 Angstroms.
B) Each head moves 10 times per second, approximately 10 Angstroms.
C) Each head moves 800 times per second, approximately 10 Angstroms.
D) Each head moves 800 times per second, approximately 110 Angstroms.
E) None of the answers is correct.

Question 28

The major family(ies) of eukaryotic motor proteins is (are)

A) myosins.
B) kinesins.
C) dyneins.
D) myosins and kinesins.
E) All the answers are correct.

Question 29

Molecules that cause bacteria to swim away from toxic substances are

A) cheomoattractants.
B) chemotaxis.
C) chemorepellants.
D) hormones
E) None of the answers is correct.

Question 30

What is the banding pattern observed in muscle cells?

Question 31

Energy used to propel molecular motors includes

A) ATP.
B) ion gradients.
C) heat.
D) light.
E) ATP and ion gradients.

Question 32

How does the length of the lever arm affect the rate?

A) A mutated shorter arm has a reduced rate.
B) A mutated longer arm has a reduced rate.
C) A mutated longer arm has a faster rate.
D) A and B are correct.
E) A and C are correct.

Question 33

What serves as the track for myosin?

Question 34

Bacterial motors differ from eukaryotic ones in that the bacterial motor

A) moves along a polymeric track.
B) moves when ATP is hydrolyzed.
C) moves when GTP is hydrolyzed.
D) spins around a central axis.
E) None of the answers is correct.

Question 35

Briefly describe the structure of myosin.

Question 36

To what other protein families are myosin, kinesin, and dynein related (in humans)?

Question 37

Binding of ATP causes ______________.

A) a decrease in kinesin affinity for microtubules
B) an increase in kinesin affinity for microtubules
C) no change in kinesin affinity for microtubules
D) cross-linking of kinesin to microtubules
E) kinesin to completely dissociate from microtubules

Question 38

The biased random walk of bacteria is the result of swimming with

A) less tumbling when Ca²⁺ levels are low.
B) more tumbling when moving toward a chemorepellant.
C) more tumbling when moving toward a chemoatractant.
D) more tumbling when ATP binds the flagellar motor.
E) None of the answers is correct.

Question 39

Human spastic paraplegia has been linked to a mutation in

A) myosin family genes.
B) kinesin family genes.
C) actin family genes.
D) dynein family genes.
E) None of the answers is correct.

Question 40

What is the energy source used to rotate the flagella?

A) ATP
B) proton gradient
C) beta oxidation
D) GTP
E) None of the answers is correct.

Question 41

What is the cause of Charcot-Marie-Tooth disease?

Question 42

What was learned using the optical trap laser studies?

Question 43

How is a bacterial motor similar to ATP synthase?

Question 44

What is F-actin?

Question 45

Is the motion of bacteria deliberate and exact toward a target chemoattractant, or is it random?

Question 46

Compare the speed of movement of a motile bacterium to a human.

Question 47

What is the "biased random walk" movement of bacteria, and when do they engage in this type of movement?

Question 48

How does the action of kinesin differ from that of myosin on its track?

Question 49

How are flagellin subunits arranged in the bacterial flagellum?

Question 50

Describe the experiment that supports the proposed role of the lever arm in myosin motor activity.