FreeMCATPrep Logo

More Than 475 Free MCAT Questions with Detailed Answers!

Click HERE for your Random Question from our MCAT Question A Day Archive

Practice MCAT Question - Q79 - Answer!

The proteins primarily responsible for preventing contraction in a resting muscle cell are

A.  myosin and troponin.
B.  myosin and tropomyosin.
C.  troponin and tropomyosin.
D.  myosin and actin.

The correct answer is (C). The troponin-tropomyosin complex binds to actin when a muscle cell is at rest so that the myosin heads (cross-bridges) cannot make contact with the active site along the actin. When calcium is released from the sarcoplasmic reticulum, the troponin-tropomyosin complex will shift to bind with calcium, thus allowing contact between the myosin heads and actin that is necessary for contraction to occur.

Check The Sidebar For Another Practice MCAT Question!! ----->