Consider this scenario: A cell biologist is studying the movement of sarcomeres
ID: 3510034 • Letter: C
Question
Consider this scenario: A cell biologist is studying the movement of sarcomeres to understand how muscle contraction is regulated. This scientist is able to culture individual muscle fibers in the laboratory for short periods of time (up to 12 hours); during this culture time, the muscle fibers remain alive and are able to respond to stimuli as they would if they were still part of a functioning muscle. Review the critical steps that are involved in muscle contraction (release of acetylcholine at the neuromuscular junction, release of calcium in the muscle fiber, active site exposure, cross bridge formation, myosin head movement, cross bridge detachment, myosin reactivation). Tell me how movement of the thin and thick filaments would be impacted I each scenario.
1. An action potential is generated in the cultured muscle fiber. At the same time, the muscle fiber is treated with a drug that prevents ATP from binding to myosin. How and why would movement of the thin and thick filaments be impacted in this scenario?
Explanation / Answer
1). Each myosin molecule contains a globular head and tail portion. The binding of ATP (adenosine triphosphate) to the head region of myosin hydrolyses the ATP to ADP (adenosine diphosphate), releasing the phosphate bond; this hydrolysis provides the energy for muscle contraction. Then the thick myosin filaments slide over the thin stationary actin filaments and cross bridges are formed.
The binding of ATP to the myosin head initiates the process of muscle contraction. The release of myosin head from the actin needs binding of another ATP molecule, otherwise the muscle remains in contracted state called, “rigor mortis.”
So, after death, the muscle remains in contracted state because of lack of ATP. The same occurs in the presence of drug that prevents ATP from binding to myosin.