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Miller's experiment


In 1950, two researchers from the University of Chicago, Stanley Miller and Harold urey, developed an apparatus in which they simulated the supposed conditions for the early Earth.

They successfully obtained results that confirmed the Oparin hypothesis.

Initially, they obtained from their experiment small molecules that over time combined to form more complex molecules, including the amino acids glycine and alanine. Subsequently, new research has obtained other amino acids and various carbon compounds.

Oparin protobionts were given different names given by scientists, depending on their content: microspheres, protocells, micelles, liposomes and coacervates. These have a double "membrane" formed by two lipid layers, similar to cell membranes.

Broadening the Oparin Hypothesis: Proteinoids and Ribozymes

In the early 1990s 1970the biologist Sidney fox heated to 60 ° C a mixture of amino acids. He obtained small polypeptides, which he called proteinoids. The water resulting from this reaction between amino acids evaporated from heating. Fox thus wanted to show that it could have been possible to combine amino acids with only one energy source, in this case heat, and without water. It was still unclear where this union might have taken place.

Scientists recently hypothesized that the synthesis of large organic molecules occurred on the surface of rocks and clay on early Earth.

Clay in particular would have been the main site of synthesis. It is rich in zinc and iron, two metals that often act as catalysts in chemical reactions. From then on, slowly the syntheses occurred, the rains would wash the earth's crust and carry the molecules into the seas, turning them into the huge organic broth suggested by Oparin. This finding, coupled with Fox's findings, solved the problem of where organic syntheses might have occurred.

There was, however, another problem: chemical reactions occur faster in the presence of enzymes. Only clay, or the metals in it, would not provide the speed needed for reactions to occur. Currently, it is suggested that an RNA molecule would have exerted enzymatic action. In addition to having international properties, RNA has also been found to have enzyme characteristics, favoring amino acid binding.

So, scientists suggest, RNAs produced on the surface of clays in the past would play the role of enzymes in the synthesis of early polypeptides. These RNAs would act as enzymes called ribozymes and their action would be aided by the zinc in the clay. Another fact that supports this hypothesis is the fact that, by placing RNA molecules in RNA nucleotide test tubes, more RNA is synthesized without the need for enzymes.