Question

You take a human smooth muscle cell and block the release of calcium from the sarcoplasmic reticulum. What effect does that have on 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 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.
E. Contraction still occurs because Ca2+ can enter the cell directly through Ca2+ channels in the plasma membrane and bind to calmodulin.

Answer 1

Answer:

The correct option is E) Contraction still occurs because Ca2+ can enter the cell directly through Ca2+ channels in the plasma membrane and bind to calmodulin.

Usually, the calcium ions are released from the sarcoplasmic reticulum of a cell during a muscle contraction, but if those are blocked, the contractions is an cell can still arise through the calcium ions which are present in the cell membrane of a cell.