What are mitochondrial fission, fusion and stress?

Mitochondrial fission is the separation of a single mitochondrion into daughter mitochondria. To achieve this, the inner and outer mitochondrial membranes must separate and then rejoin in the correct orientation, while also making sure that mitochondrial proteins and mitochondrial DNA are distributed correctly to each daughter organelle. On the other hand, mitochondrial fusion is the formation of a single mitochondrion by merging the inner and outer mitochondrial membranes of two distinct mitochondria. Mitochondrial fusion and fission occur simultaneously, and the balance between the two determines the morphology of the mitochondria.

Mitochondrial oxidative stress, which occurs when reactive oxygen species are overproduced, can lead to mitochondrial damage. Both fission and fusion help to alleviate mitochondrial stress. Fission allows damaged mitochondria to be removed, while fusion allows complementation of partially damaged mitochondria, essentially forming a functional mitochondrion.