Mitochondrial Function

Mitochondria use nutrient-derived molecules and oxygen in oxidative phosphorylation to generate much of the ATP used by many cells. They also participate in calcium handling, heat production, redox signalling, and pathways involved in cell death. Different tissues contain different numbers and types of mitochondria according to their energy and signalling demands.

Function is broader than having more or fewer mitochondria. It can refer to respiratory capacity, efficiency, membrane potential, substrate use, quality control, network shape, or the creation and removal of organelles. These features are difficult to capture in a routine blood test. Indirect measures such as VO2 max describe whole-body performance and cannot be reduced to a direct mitochondrial score.

Mitochondrial changes are discussed in metabolism, exercise, ageing, and disease. Fatigue is not a specific marker of mitochondrial dysfunction, and a wellness test should not be assumed to diagnose a mitochondrial disorder. The term is most useful when the exact tissue, method, and aspect of function are identified.

Mitochondria continually divide, fuse, move, and undergo quality-control processes. Cells can remove damaged organelles through mitophagy and generate new components through biogenesis. These dynamic processes help maintain a working network, which is why a static image or single metabolite cannot summarize the full meaning of mitochondrial function.