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13 Dec 2019

1. How does Ca2+ activate the contraction of striated skeletal muscles?

a. it binds to troponin C and causes tropomyosin to bind to the myosin binding sites on AF
b. it binds to troponin C and causes tropomyosin to move away from the myosin binding sites on AF
c. it causes phosphorylation of the myosin tail leading to myosin assembly and movement
d. it causes phosphorylation of the myosin light chain leading to myosin assembly and movement
e.

it binds to troponin C and causes tropomysin to bind to the myosin head

2. AF Treadmilling occurs when:

a. the concentration of free actin subunits is between Cc (D) and Cc (T)

b. the concentration of actin filaments is above Cc (D)

c. the concentration of free actin subunits is below Cc (T)

d. the concentration of actin filaments is below Cc (D) and Cc (T)

e. the concentration of actin filaments is between Cc (D) and Cc (T)

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Keith Leannon
Keith LeannonLv2
17 Dec 2019
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Related questions

Which of the following statements concerning cross bridges is incorrect
A. Cross bridges are globular heads of myosin molecules
B. Cross bridges have actin vining sites that are normally covered by troponin and tropomyosin except during excitatation- contraction coupling
C. Cross bridges bind with actin and then bend to pull the thin filaments inward during contraction according to the sliding filament mechanism
D. Mg2+ is necessary to bind ATP to the crops bridge
E. A fresh molecule of the ATP must be bound to the cross bridge to break the bond between actin and myosin

Determine whether each of these statements is true or false and then explain why?

a) Myosin II molecules have two motor domains and a rodlike tail that allows them to assemble into thick filaments with motor domains on either end, which is crucial for the efficient sliding of oppositely oriented actin filaments past each other.

b) When activated by Ca2+ binding, troponin C causes a conformation change in the troponin complex that allows tropomyosin molecules to shift their positions slightly so that the myosin heads can bind to the actin filaments.

c) In most animal cells, minus-end directed microtubule motors deliver their cargo to the periphery of the cell, whereas plus-end directed microtubule motors deliver their cargo to the interior of the cell. (Be sure to name these motors).

d) Both kinesin-1 and myosin II move processively making them suitably adapted for their biological functions.

e) Axonemal dyneins mediate the bending of cilia and eukaryotic flagella.

Describe the process of skeletal muscle contraction by assembling the following 10 events in the proper order. Your answer must be written in complete sentences- do not just list the letters or the events- write it out. Begin your description with an action potential traveling down a motor neuron and end with the muscle in it's relaxed state.

A) T and T system undergoes a conformational change, exposing the myosin binding sites on actin

B) myosin heads/cross bridges bind to actin and flex, shortening the sacromere

C) the motor neuron triggers an action potential at the neuromuscular junction

D) calcium ions bind to the T and T system

E) actin filaments are pulled toward the center of the sacromere, shortening the muscle fiber

F) muscle fiber is stimulated at the neuromuscular junction

G) myosin head/cross-bridges bind to actin

H) APs travel down the T-tubules to the sarcoplasmic reticulum

I) in response to an AP, calcium ions are released into the cytosol/space around the myofibrils

J) calcium ions actively transported into the sarcoplasmic reticulum

K) myosin head continues to attach, flex, release, extend, and reattach as long as calcium ions are present

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