Glossary /
Mitochondria
The organelles inside almost every cell that turn fuel and oxygen into ATP, the energy currency of life.
What it is
Mitochondria are bacteria-like organelles with their own circular DNA, evidence of an ancient symbiotic partnership. They take fatty acids, glucose, and ketones, combine them with oxygen, and produce ATP through the electron transport chain. A muscle cell can hold thousands of them; a hard-working neuron, even more.
Why it matters
Mitochondrial density and quality predict how energetic you feel and how well you age. They expand in response to demand — endurance exercise, resistance training, cold exposure, and occasional fasting all trigger mitochondrial biogenesis. They shrink and become dysfunctional under chronic overfeeding, sedentary living, and persistent inflammation. Most “metabolic” disease is, at root, mitochondrial.