Decoding the Hot-Mitochondrion Paradox.

In a 2018 paper and a subsequent article published in 2023, researchers reported that mitochondria maintain temperatures 10°C-15°C higher than the surrounding cytoplasm-a finding that deviates by five to six orders of magnitude from theoretical predictions based on Fourier's law of heat conduction. In 2022, we proposed a solution to this apparent paradox. In the present perspective, we build upon that framework and introduce new ideas to further unravel how a biological membrane-whether of an organelle or a whole cell-can become significantly warmer than its environment. We propose that ion-translocating proteins embedded in the inner mitochondrial membrane (IMM) can be modeled as ratchet engines, introducing a novel, previously overlooked mode of heat transfer. This mechanism, coupled with localized heat release during the cyclical dehydration-translocation-hydration of ions through membrane proteins, may generate transient but substantial temperature spikes. The cumulative thermal occupancy of these microscopic events across the three-dimensional surface of the IMM can account for the elevated temperatures detected by molecular probes.