a cell has plenty of energy but limited oxygen or mitochondria, it may decide to divide; while if a cell has adequate oxygen and glucose, it may just hang out. Finally, if a cell has limited energy and is getting old, it may decide to die to make room for new ones (autophagy). What signals this three-path Rubicon of fate? That’s the job of the third checkpoint, mTOR, which determines a cell’s commitment to growth, quiescence, or death.
