Mitochondria are recognized for their role in energy generation but also represent major factors in aging. Over the years, several mito-chondrial processes have been implicated in aging, but their exact role(s) in cellular longevity is often debated.Mitochondria are known to play a prominent role in the induction of apoptosis, a process that significantly contributes to the pathogenesis of age-related diseases. Also, mitochondrial respiration has been connected to aging. According to the free-radical theory of aging, reactive oxygen species (ROS) generated in mitochondria cause mutations in mitochondrial DNA (mtDNA), which lead to increasing defects in respiration and, hence, to a vicious circle of increasing mtDNA damage and ROS. However, controversy remains in this respect, as mutations in mtDNA contribute to aging but are not invariably accompanied by increased ROS.At present, the significance of mitochondrial dynamics in aging is attracting much attention. Mitochondria are very dynamic and continuously change their morphology by fission and fusion events mediated by several GTPases. When fission is affected, extensive mitochondrial networks are formed. Conversely, fusion-deficient cells contain many small organelles. An important current question is why mitochondrial morphology is so important for cell viability.
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