Sunday, March 27, 2011

Miller and Urey’s Experiment and Molecules of life


Miller and Urey’s Experiment and Molecules of life
Stanly Miller and Harold C. Urey put the Oparian-Haldane theory to test in the year1953 by recreating in the laboratory, the probable condition on the Primitive earth. They built an apparatus of glass tubes and flaska and created an atmospheres containing hydrogen, ammonia, methane and water vapour in one chamber and allowed condensed liquids to accumulate in another chamber, energy was supplied by heating the liquid containing chamber as well as by electric spark from electrodes in the gaseous chamber Miller and Urey let their experiment run continuously for about one week and then analyzed the chemical composition of the liquid inside the apparatus. To their great delight they found a large number of complex organic compound including some amino acids such glycin alkaline and aspartic acid. This so called process of abiotic synthesis of organic molecules has since then been repeated many times and scientists have recorvered most amino acids that are present, in protien molecules as well as adenine and other nucleic acid bases. The essential ‘building blokcks’     of living organisms could thus formed on the primitive earth. These results of Miller and Urey are those of numerous other scientists since, provided support for the hypothesis of Oparin and Haldane. It is now clear now why a reducing atmosphere were essential for such abiotic synthesis. Free oxygen would destroy most intermediate products in such synthesis. Thus the presence of abundant free oxygen on the earth today is thouhgt to prevent abiotic ‘origin of life’. The first photosynthetic organisms were cyanobacteri, believed to have evolved about 3300 to 3500million years ago began to release oxygen as a by product of Photosynthesis and thereby converted the earth’s atmosphere into the oxidizing one. This probably put an end to the kind of abiotic synthesis that was posible in th reducing atmosphere. Moreover, as Darwin pointed out in his letter even if some molecules are formed they would be abosorbed abd digested by the living organisms present on todays earth. All this leads to the most interesting collodion that life originated from the earths inorganic atmosphere in the past but this no longer happens today. On todays earth therefore as Luis Pasture showed life originate only from pre-existing life.
The next step in the origin of life is how these simple building blocks, were combined to form large and complex polymers such as protein and nucleic acids. In cells of the present day proteins are formed only only by the actions of the enzymes. But enzymes themselves are proteins. The early proteins and nucleic acids must, therefore have been formed by some non-enzymatic processes.
The real problem that scientists face in explaining the origin of life is how proteins and nucleic acids, that might have been formed on the primitive earth, become organized to form cells. Both Oparin and another scientist, Sydey Fox discovered that aquas suspensions of the kinds of polymers that might have been abiotically synthesized on primitive earth, when heated from spherical aggregates be seen under the microscope and remind us of bacteria and other simple unicellular organisms. The coecervates grown by absorbing molecules from their environment. They can divide by budding like bacteria. Moreover many familiar chemical reactions including the decomposition of glucose take place inside the coacervates. It is thus possible that the cells arose in much the same day as coecervates at the edges of primatives lakes and oceans. The sun provided the energy for such processes.

1 comment: