Deck 8: Contractile Proteins and Molecular Motors

Question 1

Which of the following proteins is found in a bacterial flagellum?

A)actin
B)myosin
C)flagellin
D)dynein
E)all of the above

Answer 1

C

Question 2

What type of secondary structure is most prominent in myosin?

A)antiparallel $\beta$ -sheet
B)parallel $\beta$ -sheet
C) $\alpha$ -helix
D)3₁₀ helix
E)polyproline helix

Answer 2

$\alpha$ -helix

Question 3

Which of the following is the energy source for flagellum?

A)ATP hydrolysis
B)GTP hydrolysis
C)proton gradient
D)sodium ion gradient
E)none of the above

Answer 3

C

Question 4

In muscle,thin filaments are made of _______ while thick filaments are made of _______.

A)myosin;actin
B)actin;myosin
C)myofibril;myofiber
D)myofiber;myofibril
E)none of the above

Question 5

Which form of myosin is found in striated muscle?

A)I
B)II
C)IV
D)VI
E)all of the above

Question 6

Which portion of the myosin protein found in muscle is responsible for both ATP and actin binding?

A)heavy-chain coiled-coiled tails
B)heavy-chain stalk
C)heavy-chain globular head
D)essential light chain
E)regulatory light chain

Question 7

What is the 9 + 2 array seen in the axoneme?

A)2 central microtubules ringed by 9 microtubule doublets
B)2 central microtubule doublets ringed by 9 microtubules
C)9 central microtubules with 2 microtubules attached to each central microtubule
D)9 central microtubules with 2 microtubule doublets attached to each central microtubule
E)none of the above

Question 8

Microtubules are made from which of the following proteins?

A)actin
B)myosin
C)tubulin
D)cytoplasmic dynein
E)kinesin

Question 9

Which of the following correctly describes the involvement of myosin V and kinesin in intracellular transport?

A)during transport along microtubules,both myosin V and kinesin form nonspecific interactions with tubulin
B)during transport along microfilaments,both myosin V and kinesin form highly specific interactions with actin
C)myosin V only joins with kinesin at the end of microtubules while kinesin dissociates from the myosin V-cargo complex at the start of microfilaments
D)while myosin V can aid kinesin during microtubule transport,kinesin will often disrupt myosin V during transport along microfilaments
E)none of the above

Question 10

Which protein of the thin filament is responsible for calcium binding?

A)tropomyosin
B)troponin C
C)troponin T
D)calmodulin
E)actin

Question 11

Which of the following motor proteins is correctly paired with both its binding target and its direction of movement?

A)myosin II: actin filament,moves towards (-)end
B)myosin V: actin filament,moves towards (+)end
C)kinesin: actin filament,moves towards (+)end
D)cytoplasmic dynein: microtubule,moves towards (+)end
E)axonemal dynein: microtubule,can move in either direction

Question 12

Under typical conditions within a muscle cell,the $\Delta$ G for hydrolysis of ATP is about -51 kJ/mol.If the energy required to move through one power stroke is 1.2 $\times$ 10^-20 J,what is the percent utilization of the energy from ATP hydrolysis?

Question 13

Which of the following motor proteins is correctly paired with its primary function?

A)myosin V: muscle contraction
B)myosin II: cargo transport
C)cytoplasmic dynein: bending of cilia or flagella
D)axonemal dynein: cargo transport
E)none of the above

Question 14

Which of the following correctly describes the difference between red and white muscle?

A)red muscle has considerably more mitochondria than white muscle
B)white muscle has a lower concentration of myoglobin than red muscle
C)white muscle receives much less blood flow than red muscle
D)the main source of energy in red muscle is fatty acid oxidation while in white muscle it is glycolysis
E)all of the above

Question 15

Which of the following correctly describes the organization that gives rise to muscle?

A)myofibril $\to$ sarcomere $\to$ myofiber $\to$ muscle
B)sarcomere $\to$ myofiber $\to$ myofibril $\to$ muscle
C)myofibril $\to$ myofiber $\to$ sarcomere $\to$ muscle
D)sarcomere $\to$ myofibril $\to$ myofiber $\to$ muscle
E)myofiber $\to$ myofibril $\to$ sarcomere $\to$ muscle

Question 16

In a typical cell,the use of proton gradient to power ATP synthesis requires about 3 protons for each ATP.Based on this,what is the energy expenditure,in ATP/minute,of a typical flagellum if it is running at 120 revolutions per second and requires 1000 protons to make one revolution?

Question 17

Which of the following only occurs when ATP (not ADP)is bound to the myosin head?

A)actin is released from its binding site on myosin
B)weak binding of myosin head to actin
C)strong binding of myosin head to actin
D)power stroke of muscle contraction
E)none of the above

Question 18

Which of the following is the best description of how actin and myosin work in cooperation to allow muscle contraction?

A)myosin head groups push against actin filaments to lengthen the sarcomere
B)myosin head groups walk along the actin filament to shorten the sarcomere
C)myosin head groups interact with actin only when the sarcomere is fully lengthened
D)all myosin head groups move along the actin filament simultaneously to shorten the sarcomere
E)none of the above