Decoding the Hot-Mitochondrion Paradox.

In a 2018 paper and a subsequent article published in 2023, researchers reported that mitochondria maintain temperatures 10-15 degrees higher than the surrounding cytoplasm - a finding that deviates by 5 to 6 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 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. In the case of protons, the cycle additionally includes deprotonation before translocation and protonation after. The cumulative effect of these microscopic events across the three-dimensional surface of the IMM can account for the elevated temperatures detected by molecular probes. We also offer a hypothesis based on quantum chemical calculations on how such probes might detect these fleeting thermal signatures.