When animals die, the lack of ATP causes muscles to stiffen in rigor mortis because
A) muscles cannot contract without ATP.
B) actin and myosin cannot bind without ATP.
C) actin and myosin cannot separate without ATP.
D) ATP is required for synthesis of protein filaments.
E) ATP forms cross-bridges between filaments.

Question

Quizplus · Accepted Answer

Actin and myosin filaments are strongly bound in rigor mortis because they cannot separate without the input of ATP. During life, ATP is required to release the myosin head from the actin filament between muscle twitches, so without ATP, the myosin heads remain bound and the muscle becomes stiff.

When Animals Die, the Lack of ATP Causes Muscles to Stiffen