Muscle Fiber Contraction and Calcium

[Soaring Crane]

When glycerinated rabbit muscle fiber was placed in 10^-4 M of CaCl2 solution, the percent change in length of the muscle fiber was around 93%.

When glycerinated rabbit muscle fiber was placed in 30 mM ATP in 10^-2 M CaCl2 + 0.05 M KCl + 0.001 M MgCl2 solution, the percent change in length of the muscle fiber was around 51%.

Why does the first trial (with just the calcium ions) experience a greater contraction than the second solution with both ATP and calcium ions?

Thank you for any replies.

 

[Nino MMP]

The greater contraction in the first trial is likely due to the higher concentration of calcium ions, which are known to play a key role in muscle contraction. ATP, on the other hand, is necessary for the energy needed to power muscular contraction, but its presence alone may not be enough to cause significant contraction.

 

[Blueshift5]

The first trial with just calcium ions resulted in a greater contraction because calcium ions are essential for muscle fiber contraction. When calcium ions bind to the protein complex troponin, it triggers a series of events that leads to muscle contraction. In the absence of ATP, the muscle fiber is still able to contract to a certain extent due to the presence of calcium ions.

In the second trial with both ATP and calcium ions, the presence of ATP allows for a more controlled and sustained muscle contraction. ATP provides the energy needed for the muscle fibers to contract and relax in a coordinated manner. Therefore, the percent change in length of the muscle fiber is lower compared to the first trial because the muscle fibers are able to maintain a steady level of contraction with the help of ATP.

In summary, the first trial experienced a greater contraction because calcium ions alone can trigger muscle fiber contraction, but the addition of ATP in the second trial allows for a more controlled and sustained contraction.