Life’s Building Blocks May Have Arisen Simultaneously
by Janet Fang
Photo credit: Artwork showing a rocky planet being bombarded by comets / NASA/JPL-Caltech
Chemists have shown how many of life’s most basic building blocks could have arisen during a single set of chemical reactions with just two simple compounds and some sunlight.
At its most basic, a cell is comprised of three subsystems: a compartment-forming system of fatty lipids to keep its contents contained, a metabolic system with catalysts and enzymes, and some way to pass on information like DNA or single-stranded RNA. These genetic molecules contain instructions for making proteins, an essential part of all organisms alive today. However, modern cells can’t replicate DNA or RNA without proteins, Science explains, and they can’t synthesize lipids without protein-based enzymes encoded by genetic material either. Now, researchers say they may have solved this conundrum, the original chicken-or-the-egg paradox.
One major question that comes up when studying the origin of life is: Did the subsystems emerge together all at once, or one after the other when life first began? By experimenting with the assembly of various biomolecular building blocks, a Cambridge team led by John Sutherland found that precursors of RNA, amino acids (which make up proteins), and lipids can all be derived from hydrogen cyanide. All cellular subsystems could have arisen simultaneously though chemical reactions driven by ultraviolet light; the only other thing you need is hydrogen sulfide to donate an electron. Some metal-containing minerals may have helped catalyze the process.
Early Earth was a favorable setting for those reactions, Sutherland explains to Science, and both hydrogen cyanide and hydrogen sulfide were common in those days: The comets that bombarded the planet for the first several hundred million years carried hydrogen cyanide with them, and those impacts could have also produced the energy needed to synthesize the compound from hydrogen, carbon, and nitrogen.
However, it’s possible that slight variations in chemistry and energy created amino acids or lipids, for example, in different places, he adds. In that case, all of those compounds probably met up after the rain washed them into the same puddles.
The findings were published in Nature Chemistry