mitochondrialsupporting

Mitochondria are double-membrane-bound organelles found in most eukaryotic cells. The standard plural is mitochondria; forms such as "mitochondrials" are not used in scientific writing. They are best known as the cellular powerhouses, generating ATP through oxidative phosphorylation. The inner membrane folds into cristae, increasing surface area for enzymes of the respiratory chain. Mitochondria contain their own circular DNA and ribosomes, and they can replicate semi-autonomously within the cell.

Most mitochondrial proteins are encoded in the cell nucleus and imported into the organelle via translocase complexes such as TOM and TIM. The human mitochondrial genome is a small, circular DNA molecule that encodes 13 essential polypeptides of the respiratory chain, along with rRNAs and tRNAs required for mitochondrial translation.

In metabolism, mitochondria convert energy from nutrients into ATP, supply intermediates for biosynthesis, and help regulate calcium storage. They are also sources of reactive oxygen species and participate in programmed cell death through pathways involving cytochrome c release and caspase activation.

Mitochondrial quality is maintained by dynamics and turnover. Mitochondria continually undergo fission and fusion, and damaged organelles are removed by mitophagy. In most animals, mitochondria are inherited maternally. They divide and grow during the cell cycle but keep a fixed complement within a cell.

Evolutionarily, mitochondria are believed to derive from an ancient endosymbiotic event with an alpha-proteobacterium. Dysfunction of mitochondria—whether via mtDNA mutations or nuclear gene defects—underpins various disorders, including Leber hereditary optic neuropathy, MELAS, and many forms of mitochondrial myopathy and neurodegeneration. mtDNA mutations can accumulate with age and influence cellular aging.

Because of their central role in energy metabolism, mitochondria are a focus in studies of cancer, metabolic diseases, and aging, with research spanning bioenergetics, genetics, and therapeutic strategies to preserve mitochondrial function.