A group of rats are bred in a laboratory to study muscle function. This group possesses a genetic defect that causes troponin to be incorrectly synthesized, making it non-functional. Because of this, the rats are entirely paralyzed. Which of the following correctly explains the impact of the defect on the muscle?
A)Troponin can't bind Ca⁺², which stops tropomyosin from pulling away to reveal actin binding spots on the thin filament.
B)Troponin, when revealed by tropomyosin, won't be able to bind to the myosin heads of the thick filament.
C)Troponin won't pull away to reveal the actin binding spots of the thin filament after tropomyosin binds Ca⁺².
D)Troponin, when revealed by actin, won't be able to bind to the myosin heads of the thick filament.

Question

Quizplus · Accepted Answer

Troponin is responsible for binding calcium ions, which causes a conformational change that allows tropomyosin to move away from the myosin binding sites on actin. This allows myosin heads to bind to actin and begin the cross-bridge cycling that leads to muscle contraction. If troponin cannot bind calcium, tropomyosin remains in its blocking position, preventing the myosin heads from accessing the actin binding sites and leading to muscle paralysis.

A Group of Rats Are Bred in a Laboratory to Study