The production of ATP using energy from the electrochemical gradient is perfected with the evolution of the enzyme ATP synthase, found within all life today. Some protocells started using ATP as well as acetyl phosphate and pyrophosphate. This ancient enzyme is still found in many bacteria and archaea, the first two branches on the tree of life. The evolution of an enzyme called pyrophosphatase, which catalyses the production of pyrophosphate, allowed the protocells to extract more energy from the gradient between the alkaline vent fluid and the acidic ocean. The earliest protocells may have been elusive entities, though, often dissolving and reforming as they circulated within the vents. Some of these bubbles would have enclosed self-replicating sets of molecules – the first organic cells. 6.įatty molecules coated the iron-sulphur froth and spontaneously formed cell-like bubbles. Evolution got under way, with sets of molecules capable of producing more of themselves starting to dominate. Thermal currents and diffusion within the vent pores concentrated larger molecules like nucleotides, driving the formation of RNA and DNA – and providing an ideal setting for their evolution into the world of DNA and proteins. These molecules drove the formation of amino acids – the building blocks of proteins – and nucleotides, the building blocks for RNA and DNA. The electrochemical gradient between the alkaline vent fluid and the acidic seawater leads to the spontaneous formation of acetyl phosphate and pyrophospate, which act just like adenosine triphosphate or ATP, the chemical that powers living cells. Similar iron-sulphur catalysts are still found at the heart of many proteins today. Some of these reactions were catalysed by the iron-sulphur minerals. Inside the iron-sulphur bubbles, hydrogen reacted with carbon dioxide, forming simple organic molecules such as methane, formate and acetate. When upwelling hydrothermal fluids reacted with this primordial seawater, they produced carbonate rocks riddled with tiny pores and a “foam” of iron-sulphur bubbles.
Unlike today’s seas, the early ocean was acidic and rich in dissolved iron.
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