Question-4 Can simple molecules and kinetic energy lead to chemical evolution? Elaborate what experiment supports this hypothesis and infer your results for the same.
Question-4 : Can simple molecules and kinetic energy lead to chemical evolution? Elaborate what experiment supports this hypothesis and infer your results for the same.
Answer :
According to prevalent theory, chemical evolution occurred in four stages. In the first stage of chemical evolution, molecules in the primitive environment formed simple organic substances, such as amino acids. This concept was first proposed in 1936 in a book entitled, “The Origin of Life on Earth,” by the Russian scientist, Aleksandr Ivanovich Oparin (1894– 1980). He considered hydrogen, ammonia, water vapor, and methane to be components in the early atmosphere. Oxygen was lacking in this chemically-reducing environment. Oparin stated that ultraviolet radiation from the Sun provided the energy for the transformation of these substances into organic molecules. Scientists today state that such spontaneous synthesis occurred only in the primitive environment. Abiogenesis became impossible when photosynthetic cells added oxygen to the atmosphere. The oxygen in the atmosphere gave rise to the ozone layer, which then shielded Earth from ultraviolet radiation. Newer versions of this hypothesis contend that the primitive atmosphere also contained carbon monoxide, carbon dioxide, nitrogen, hydrogen sulfide, and hydrogen. Present-day volcanoes emit these substances.
In 1957, Stanley Miller (1930–) and Harold Urey (1893–1981) provided laboratory evidence that first-stage chemical evolution as described by Oparin could well have occurred. Miller and Urey created an apparatus that simulated the primitive environment. They used a warmed flask of water for the ocean and an atmosphere of water, hydrogen, ammonia, and methane. Sparks discharged into the artificial atmosphere represented lightning. A condenser cooled the atmosphere, causing rain that returned water and dissolved compounds back to the simulated sea. When Miller and Urey analyzed the components of the solution after a week, they found various organic compounds had formed. These included some of the amino acids that compose the proteins of living things. Their results gave credence to the idea that simple substances in the warm primordial seas gave rise to the chemical building blocks of organisms.
In the second stage of chemical evolution, the simple organic molecules (such as amino acids) that formed and accumulated joined together into larger structures (such as proteins). The units linked to each other by the process of dehydration synthesis to form polymers. A problem with this part of the hypothesis was that the abiotic synthesis of polymers had to occur without the assistance of enzymes. In addition, these reactions give off water and would, and would therefore not occur spontaneously in a watery environment. Sydney Fox of the University of Miami suggested that waves or rain in the primitive environment splashed organic monomers on fresh lava or hot rocks, which would have allowed polymers to form abiotically. When he tried to do this in his laboratory, Fox produced proteinoids—abiotically synthesized polypeptides.
In the third step in chemical evolution, it is suggested, polymers interacted with each other and organized into aggregates known as protobionts. Protobionts are not capable of reproducing, but had other properties of living things. Scientists have successfully produced protobionts from organic
In the second stage of chemical evolution, the simple organic molecules (such as amino acids) that formed and accumulated joined together into larger structures (such as proteins). The units linked to each other by the process of dehydration synthesis to form polymers. A problem with this part of the hypothesis was that the abiotic synthesis of polymers had to occur without the assistance of enzymes. In addition, these reactions give off water and would, and would therefore not occur spontaneously in a watery environment. Sydney Fox of the University of Miami suggested that waves or rain in the primitive environment splashed organic monomers on fresh lava or hot rocks, which would have allowed polymers to form abiotically. When he tried to do this in his laboratory, Fox produced proteinoids—abiotically synthesized polypeptides.
In the third step in chemical evolution, it is suggested, polymers interacted with each other and organized into aggregates known as protobionts. Protobionts are not capable of reproducing, but had other properties of living things. Scientists have successfully produced protobionts from organic
millers experiment
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