The Chemosynthetic theory , Also known as biosynthetic theory or physicochemical theory of the origin of life, is based on the hypothesis that life on our planet originated from the grouping (synthesis) of very primitive molecules at the origin of time and were Complexing to form the first Cells .
This theory was developed almost at the same time - between 1924 and 1928 - but separately by scientists Alexander I. Oparin (Russian biochemist) and John B.S. Haldane (English biologist), confirming the Big Bang theory and overturning the theory of spontaneous generation, a belief prevalent since antiquity.
Among the contributions to the work of these two scientists, the participation of the Mexican pharmacist Alfonso Luis Herrera, who made studies on the origin and evolution of life on earth and who is considered the creator of plasmogenia, Studies the origin of protoplasm, that is, the origin of life.
His studies were published abroad and served as a basis for Oparin and Haldane to develop their theory Which was also supported by geological, paleontological and biochemical studies.
At present, the chemosynthetic theory is the most accepted by scientists. It explains the origin of life from the chemical evolution and the physical phenomena of matter.
The Chemosynthetic Theory: How Did Life Come On Earth?
According to the Big Bang theory, the earth arose about 5,000 million years ago from a cloud of hydrogen gas. Simultaneously the sun and the other planets of the solar system originated.
At first, the temperature of the earth was extremely high, but little by little it cooled and the primitive oceans began to form.
At that time, the atmosphere was very different from the current one. Water vapor, methane, ammonia, carbon dioxide and hydrogen prevailed.
Unlike what happens in our days, in that initial phase the ozone layer did not exist, reason why all type of radiations arrived at the surface of the earth, including the ultraviolet rays and the infrared.
In addition, there was a lot of energy produced by constant volcanic eruptions, lightning and lightning.
Under this scenario it is quite possible that the first organic compounds in these primitive oceans, among which were carbohydrates, lipids and some amino acids, have formed and destroyed again and again until finally they find some stability to evolve.
For millions of years these substances were chemically combining with each other, forming increasingly complex substances that were delimited by a membrane.
To these substances, Oparin I call them protobiontes. Their existence lasted for millions of years and, with the passage of time, acquired characteristics of living beings, performing functions such as nutrition and excretion. They also began to reproduce, which implied the appearance of nucleic acids carrying the genetic information.
Evolutionarily, the protobionts preceded the first simple and simple cells that emerged thousands of years later. It is believed that the first living beings that appeared on earth were very similar to bacteria.
These extremely simple primordial beings were evolving and becoming complexed to become multicellular organisms.
The contribution of Miller and Urey
In 1953, American chemists Stanley L. Miller and Harold Clayton Urey attempted to reproduce in a laboratory the conditions suggested by Oparin and Haldane in their theory. Miller and Urey created an apparatus in which they reproduced the conditions of the primitive earth raised by the chemosynthetic theory.
The apparatus consisted of several containers connected together. In order to recreate the conditions of the earth's original atmosphere, these scientists placed water, methane, ammonia and hydrogen in the two electrodes.
By means of the electrodes they produced electrical discharges that made to jump sparks similar to the ones generated by the lightning.
The water that simulated the primitive oceans was brought to the point of boiling. In it were introduced a multitude of inorganic molecules from which simple and simple living beings had to be formed.
The experiment continued for several weeks, at the end of which the scientists noticed that some substances had accumulated in the water and in the walls of the containers.
When analyzing them, Miller and Urey realized that they were several organic compounds, including four different amino acids, which are involved in the formation of proteins.
With their experiment, American scientists were able to verify that organic compounds were formed from inorganic compounds.
In this way they opened the way to demonstrate that pre-biological evolution, as posed by Oparin and Haldane, was possible.
Since then, experiments similar to those of Miller and Urey have been carried out, but varying the quantities and types of gases. Also, in some experiments different energy sources such as infrared and ultraviolet rays have been used.
Most of these experiments obtained great diversity of organic compounds that are part of living beings.
In this way, the chemosynthetic theory has been partially verified.
Limitations for verification
Experiments carried out to verify chemosynthetic theory have succeeded in demonstrating that the origin of life is likely to have been as described by Oparin and Haldane. However, it can not be overlooked that this happened over billions of years.
Due to this long period of time, which covered the process of the emergence of life on earth, it is impossible to reproduce it fully and faithfully within the laboratories.
The obstacle of time has made scientists face a difficult scenario, because it may never be possible to know exactly how the first organisms that inhabited the planet formed.
In spite of this inconvenience, the chemosynthetic theory has allowed to draw a picture quite close to what could have been the genesis of life on Earth.
References
- Paula Andrea Giraldo. Chemosynthetic theory of the origin of life. Retrieved from www.calameo.com.
- Physicochemical theory of the origin of life. Recovered from academia.edu.