We discuss why the membrane potentials of cancer cells are often smaller than those of healthy cells, and why the stresses associated with reduced membrane potentials might not automatically cause destruction of cells by apoptosis.The fact that cytochrome c appears as a key intermediary both in cellular respiration and in apoptosis suggests that damage to cytochrome c, or failure to express it, might reduce ion pumping across the cell membrane, thus diminishing the cellular membrane potential, whilst simultaneously damaging a key apoptosis pathway. Degraded respiration will also force the cell to obtain energy from glycolysis, consistent with the Warburg Hypothesis.