Which statement about actin is true?
A) Two strands of tropomyosin are twisted around polymerized actin.
B) Actin carries out the power stroke motion that allows filaments to slide during contraction.
C) Actin is the only protein making up thin filaments in a muscle fiber.
D) Troponin forms the head of the actin molecule.
E) Tropomyosin has ATPase activity and interacts with the actin.

Question

Quizplus · Accepted Answer

Two strands of tropomyosin are indeed twisted around polymerized actin.

Answer: B 
 Actin does not carry out the power stroke motion, but rather myosin does.

Answer: C 
 Actin is not the only protein making up thin filaments in a muscle fiber, as tropomyosin and troponin are also present.

Answer: D 
 Troponin does not form the head of the actin molecule.

Answer: E 
 Tropomyosin does not have ATPase activity, but it does interact with actin.

Which Statement About Actin Is True