Clearing damaged biomolecules is important, however our bodies do it normally. Even amyloid proteins are degraded by native cells. Previous study showed some extension of mouse life span by mitochondrial catalase. According to the result, however, there still is a significant damage in mtDNA. This might be because mtDNA is attached to matrix side of the inner membrane, thus decreasing the effectiveness of the catalase. More importantly perhaps, just next to the mtDNA is the inner membrane which embeds respiratory complexes as direct source of leaking electrons and worse the catalase cannot permeate the membrane. Thus it seems crucial to protect the membrane from oxidative insult. The putative protection of the membrane is crucial if and only if the damage is faster than turnover.