Figure 3.

Biological origin of free radicals and their effect on cell viability. Reactive Oxygen Species (ROS) are generally derived both from intrinsic factors (enzymatic reactions physiologically conducted in subcellular organelles) and from the numerous extrinsic ones. Although ROS evidently remain essential for normal functioning of the cell, including immune response or redox signaling, their overload may prove harmful and cause significant damage. Ultimately, it may lead to execution of apoptotic or necrotic cell death or even drive tumor growth. Unfolded Protein Response (UPR) signaling pathway is closely linked to ROS-induced oxidative stress and it becomes activated to address cellular redox imbalance.