Final answer:
The claim that skeletal muscle cells are entirely depleted of stored ATP at exhaustion is false. Muscles maintain a small reserve of ATP, using alternative metabolic pathways to prevent the complete depletion of ATP and avoid rigor-like states during intense activity.
Step-by-step explanation:
The statement that skeletal muscle cells are completely depleted of stored ATP at the point of exhaustion is false. While it is true that ATP is essential for skeletal muscle contraction, with ATP needed for myosin heads to release from actin and for pumping calcium ions back into the sarcoplasmic reticulum, muscles do not completely deplete their ATP even at exhaustion. Some ATP must remain to prevent muscles from entering a state of rigor, as observed in rigor mortis postmortem. During intense exercise leading to fatigue, the body utilizes other pathways, such as creatine phosphate metabolism and anaerobic glycolysis, to replenish ATP. A small reserve of ATP is maintained to allow for basic functions such as the detachment of myosin heads from actin, preventing the rigidity associated with rigor mortis.