Answer:
Even after block the release of calcium from the sarcoplasmic reticulum ,the contraction still occurs.
The reason is that the calcium ions (Ca+2) can enter the cell directly through L-type voltage gated Calcium channels in the plasma membrane and bind to calmodulin ,forming calcium-calmodulin complex.
Explanation:
The contraction in smooth muscle is quiet different than that in the skeletal muscle. ( In the smooth muscles , calcium enters from outside as well alongwith the calcium coming from sarcoplasmic reticulum while in skeletal muscles , calcium comes only from the sarcoplasmic reticulum )
In the case of smooth muscle , the L-type voltage-gated calcium channels are located on the plasma membrane of smooth muscle cells. As these channels open , the calcium ions rush inside the smooth muscle cell and bind the calmodulin forming the calcium calmodulin complex. This complex then binds to the myosin light chain kinase enzyme and causes the phosphorylation of the myosin light chains resulting in the contraction.
When the release of the calcium is blocked from the sarcoplasmic reticulum then the contraction of the smooth muscle cells still continues and will not get stopped. Thus, option E is correct.
The complete question is: You take a human smooth muscle cell and block the release of calcium from the sarcoplasmic reticulum. What effect does that have on the contraction of that smooth muscle cell, and why?
A. Contraction is completely blocked because calcium binding to troponin is required for contraction.
B. Contraction still occurs because Ca2+ can enter the cell directly through Ca2+ channels in the plasma membrane and bind to troponin.
C. Contraction is completely blocked because calcium binding to calmodulin is required for contraction.
D. Contraction still occurs because the contraction in smooth muscle is completely independent of Ca2+ levels.
E. Contraction still occurs because Ca2+ can enter the cell directly through Ca2+ channels in the plasma membrane and bind to calmodulin.
Smooth muscles are spindle-shaped muscles that have an elongated nucleus and are present in the organs like the liver, intestines, and the pancreas. The calcium ions enter the muscle cells directly through the L-type voltage-gated calcium channels.
The calcium from the outside of the cells enters the smooth muscles and binds with the calmodulin resulting in the calcium calmodulin complex. This further gets binds to the kinase enzyme and initiates the phosphorylation leading to the contraction.
Therefore, option E. the blocking of the calcium does not stop the contraction.
Learn more about calcium channels here:
https://brainly.com/question/14693523
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