The Perplexing Chronicles of Bioenergetics
The Perplexing Chronicles of Bioenergetics
Making a Living, Now and in the Past
All biological operations require the input of energy. In contemporary organisms, energy is harvested by mechanisms that are essentially electrical. Energy transduction relies on the circulation of ions across membranes (usually protons), and on a sophisticated rotary ATP synthase to capture the energy and conserve it as ATP. This chapter begins with an overview of chemiosmotic energy transduction and then poses the question, How did LUCA make a living? Current thinking questions the traditional notion that that LUCA lived off prebiotic organic molecules, and favors geochemical processes, such as the reduction of CO2 by hydrogen gas. One possible habitat for such organisms would be mineral honeycombs laid down by hydrothermal vents. If there is any truth to this hypothesis, then chemiosmotic energy transduction will have been part of LUCA's endowment, and may have evolved under the special circumstances that prevail in those vents. Subsequent evolution will have led to the liberation of cells from their mineral cradle, and the progressive expansion of energy metabolism by the invention of both photosynthesis and respiration.
Keywords: chemiosmotic energy coupling, proton circulation, membranes, ATP synthase, hydrothermal vents, respiration, photosynthesis
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