Thermosynthesis by biomembranes: energy gain from cyclic temperature changes.

A theoretical mechanism is described allowing biomembranes to convert heat into electrical energy during temperature cycling (thermosynthesis). Necessary conditions for thermosynthesis are a temperature dependent electrical capacity and a conductivity as low as that of artificial lipid bilayers. Temperature cycling, and consequently thermosynthesis, can take place in leaves during cyclic transpiration and in organisms in natural waters that are carried along by convection currents. Electrogenic ATPases can convert the electrical energy gained by thermosynthesis into ATP if their activity and stoichiometry are properly regulated. The power of thermosynthesis is discussed and its possible value compared with the power of respiration. Environments where thermosynthesis may occur are listed. Thermosynthesis is a plausible energy source for the first living organisms.