Table 2. Molecular Systems of Stress Response.

Stress response is mediated by at least five highly interconnected molecular systems. Both severe stress and contradictory growth signals can activate programmed cell death [i.e., apoptosis; see Table 1; Kroemer et al. 2010].

Molecular Systems	Functions
1. Antioxidant defenses	Regulate effects of reactive species and redox signaling
2. Xenobiotic metabolism	Increases the solubility of an exogenous chemical to facilitate its removal
3a and 3b. DNA repair and cell cycle pathway	Prevent disruption of normal cell function and development caused by chromatin denaturation and delay certain synthetic processes in the cell cycle until other processes, such as DNA repair, are complete
4. Unfolded protein response	Prevents an accumulation of misfolded and unfolded proteins in the endoplasmic reticulum lumen
5. Autophagy	Degrades cytoplasmic components (including mitochondria) through the lysosome for quality-control