Biochemistry 4th Edition by Christopher Mathews,Kensal van Holde, Dean Appling, Spencer Anthony Cahill

Exercise 5

A few hours after the death of an animal the corpse will stiffen as a result of continued contraction of muscle tissue (this state is called rigor mortis ). This phenomenon is the result of the loss of ATP production in muscle tissue.
(a) Consult Figure 8.11 (page 292) and describe, in terms of the six-step model of muscle contraction, how a lack of ATP in sarcomeres would result in rigor mortis.
(b) The Ca 2+ transporter in sarcomeres that keeps the [Ca 2+ ]~10 7 M requires ATP to drive transport of Ca 2+ ions across the membrane of the sarcoplasmic reticulum. How would a loss of this Ca 2+ transport function result in the initiation of rigor mortis
(c) Rigor mortis is maximal at ~12 hrs after death, and by 72 hrs is no longer observed. Propose an explanation for the disappearance of rigor mortis after 12 hrs.