An enzyme still toiling away in modern bacteria contains signatures of the prebiotic world, suggesting that it originated in the very earliest cells. The enzyme unlocks energy from a simple molecule called pyrophosphate, and its discovery bolsters the idea that this was how primitive life first got its energy. The universal energy currency in modern cells is a molecule called ATP. It contains a high-energy bond between two phosphate groups that supplies energy when it is broken. But ATP is a complex organic molecule, and scientists wondered how primitive cells struggling to function as life emerged could have developed such a complicated mechanism. Almost 40 years ago, Fritz Lipmann, the scientist who first worked out the role of ATP, suggested that the original energy carrier might instead have been pyrophosphate. This molecule, found in cooling lava, consists simply of two phosphate groups joined with a high-energy bond. Some photosynthetic bacteria still use pyrophosphate as a secondary energy source. They absorb phosphate from their environment and use sunlight to create a phosphate bond, linking the molecules into pyrophosphate. Breaking the bond provides the organism with energy when and where in the cell it is needed. If this simple mechanism came first it could have paved the way for ATP.
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