Muscle Contraction and Locomotion

Art Connections

Figure Which of the following statements about muscle contraction is true?

  1. The power stroke occurs when ATP is hydrolyzed to ADP and phosphate.
  2. The power stroke occurs when ADP and phosphate dissociate from the myosin head.
  3. The power stroke occurs when ADP and phosphate dissociate from the actin active site.
  4. The power stroke occurs when Ca2+ binds the calcium head.

Hint:

Figure B

Figure The deadly nerve gas Sarin irreversibly inhibits acetycholinesterase. What effect would Sarin have on muscle contraction?

Hint:

Figure In the presence of Sarin, acetycholine is not removed from the synapse, resulting in continuous stimulation of the muscle plasma membrane. At first, muscle activity is intense and uncontrolled, but the ion gradients dissipate, so electrical signals in the T-tubules are no longer possible. The result is paralysis, leading to death by asphyxiation.