Urey and Miller Experiment Method

In this Urey and Miller experiment method post we have briefly explained about Formation of Protobionts, and urey and miller experiment method.

Urey and Miller Experiment Method

The urey and miller experiment method was the first attempt to scientifically explore ideas about the origin of life. The purpose was to test the idea that the complex molecules of life (in this case, amino acids) could have arisen on our young planet through simple, natural chemical reactions.

Formation of Protobionts

Abiotically produced molecules can spontaneously self-assemble into droplets that enclose a watery solution and maintain a chemical environment different from their surroundings.

Scientists call these spheres as ‘protobionts’. Liposomes are lipids in a solution that can self-assemble into a lipid bilayer. Some of the proteins inside the liposomes acquired the properties of enzymes resulting in fast multiplication of molecules.

The coacervates with nucleoprotein and nutrients had a limiting surface membrane that had the characters of a virus or free living genes. Subsequently number of genes united to form ‘proto viruses’ somewhat similar to present day viruses. Two major cell types that appeared during this time were significant.

One form of the earliest cell contained clumps of nucleoproteins embedded in the cell substance. Such cells were similar to the Monera. They are considered as ancestral to the modern bacteria and blue green algae. The other form of earliest cells contained nucleoprotein clumps that condensed into a central mass surrounded by a thin membrane.

This membrane separated nucleoproteins from the cell substances. Such cells were referred to as Protista. When the natural sources of food in the ocean declined in course of time the ancestors of Monera and Protista had to evolve different methods for food procurement.

These may be summarized as parasitism, saprophytism, predator or animalism and chemosynthesis or photosynthesis. When the number of photosynthetic organisms increased there was an increase in the free O2 in the sea and atmosphere.

The atmospheric oxygen combined with methane and ammonia to form CO2 and free nitrogen. The presence of the free O2 brought about the evolution of aerobic respiration which could yield large amounts of energy by oxidation of food stuffs. Thus Prokaryotes and Eukaryotes evolved.

Urey and Miller Experiment Method

The building blocks of life have been discovered and characterized since the early 19th century. Regarding the synthesis of molecules of prime interest to the origin of life, two major achievements shall be given.

In 1850, Adolf  Strecker succeeded in the first laboratory synthesis of an amino acid: alanine from a mixture of acetaldehyde (CH3CHO), ammonia (NH3), and hydrogen cyanide (HCN).

A few years later, in 1861, Alexandr  Butlerov performed the first laboratory synthesis of sugar mixtures (also known as the formose reaction) from formaldehyde (HCHO) using a strong alkaline catalyst (NaOH).

Although these discoveries were very interesting, they were not linked to the origin-of-life problem. Hence, little progress was made in finding a scientific description of the origin of life was introduced by Aleksandr  Ivanovich Oparin.

Oparin introduced the concept of chemical evolution, which could be seen as the roots of the Darwin theory of evolution. In this concept, life was the result of successive spontaneous chemical reactions that produce increasingly complex chemical structures. He suggested that such chemical evolution would take place within an oxidizing atmosphere of the primitive Earth.

Urey and Miller Experiment

Urey and Miller Experiment Method System setup

After sometime he made some modifications in his early concepts and changed the early atmosphere to a highly reducing environment. Similar ideas were simultaneously given by the English biologist John Haldane, who was the first to mention the concept of a “prebiotic soup” where chemical evolution took place.

Oparin and Haldane’s ideas were expressed at a theoretical level only. The urey and miller experiment method confirmation of the theory of chemical evolution was provided in 1953 by Stanley Miller and Harold Clayton Urey. They conceived and built an urey and miller experiment method to simulate a putative primitive Earth environment.

In this urey and miller experiment method a gaseous mixture of hydrogen (H2), methane (CH4), ammonia (NH3), and water (H2O) was exposed to an electric discharge that simulated that of storm lightning.

The mixture was connected to a bulb filled with liquid water that could be heated. It was found that within a week 15% of carbon originally present as methane had converted into other simple carbon compounds.

Among these compounds was formaldehyde (HCHO), hydrogen cyanide (HCN). These compounds then combined to form simple molecules, such as formic acid (HCOOH) and urea (NH2CONH2) and more complex molecules containing carbon-carbon bonds including the amino acids glycine and alanine.

The resulted production of a large amount of organic molecules, including several amino acids was the urey and miller experiment method proof of the theory of chemical evolution.

This urey and miller experiment method showed that the chemistry between simple molecules, which were abundant in the atmosphere of the primitive Earth, led to the synthesis of key compounds that in turn might have led to the forms of life on Earth.

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