Free radical damage has long been suspected as a culprit in aging, and mitochondria are both the primary source of free radicals in a cell and the main protection against them.

• 长久以来，科学家一直怀疑自由基损伤是老化的罪魁，而且线粒体既是细胞内自由基的主要来源，也是防御自由基的主要屏障。