Cells protect themselves against cellular stress through several different mechanisms. For example, autophagy, activation of cell cycle arrest, apoptosis, and the heat shock response.

• Autophagy is triggered when there is nutrient starvation and oxidative stress. Its purpose is to recycle cellular components and damaged organelles.
• The activation of cell cycle arrest is for creating a stopping point in the cell cycle, where duplication and division is stopped to prevent any further damage.
• The heat shock response helps protect a cell against damage by acting as chaperons in protein folding, ensuring that proteins do not misfold and keep their required shape.  If the previous methods fail to protect the cell, it will initiate apoptosis as the cell has experienced too much damage or is too old.