What does the theory of the origin of life from the pond say?
The first, most famous model of the origin of life on
Such bodies of water appeared on the surface of the planet during the fall of comets and meteorites several million years before the primary ocean arose on it.
And until the end of the 70s of the XX century, until they took placethose same deep-sea expeditions to faults, this hypothesis was the most popular. Other early 20th century scientists, such as John Haldane and Alexander Oparin, agreed with Darwin and developed his theory.
They independently assumed thatthe young Earth had a "restorative" atmosphere, that is, antagonistic to the one where oxygen is produced. In such an atmosphere, for example, iron will never rust. The atmosphere of that time may have been saturated with methane and ammonia, forming an ideal “primordial soup” from which life emerged in some shallow body of water.
This theory is supported by the fact that onThe land surface contained a number of critical elements for life, for example, molybdenum, boron and nitrogen, the concentration of which in the primary ocean was extremely low.
How did they try to prove the theory?
In order for the first organism to appear, there must be cells, at least one.
According to scientists, the appearance of a cellcontributed to the accumulation of organic substances in the environment and the emergence of prebiotic forms - protocells, which have become a connecting link between living and nonliving matter. However, these protocells are no longer on earth. But scientists know that they definitely should have contained:
- self-replicating molecule with hereditary information;
- a shell that protects it from the environment.
Analogues of protocells were synthesized in 2011biologists at the University of Tokyo. As a result of the polymerase chain reaction (PCR), it was possible to achieve their full spontaneous division - similar to what happens in natural conditions.
In order to prepare the primary substrate,or, in other words, coacervate, the authors of the work took dozens of organic components, the ratio of which was previously calculated on a computer. Having combined, these substances formed coacervate vesicles in the substrate with a cationic shell and DNA elements inside.
However, this was still not enough toconfirm that living things can come from non-living things. DNA is not capable of self-reproduction without the participation of certain enzymes - specific proteins that catalyze all stages of its replication. Japanese scientists managed to create it in the laboratory, but, again, using biological components.
What was the material for the first life?
A new study by an international group of scientists was designed to find potential mechanisms for the formation of the first cells "from scratch" - only during chemical processes, without the participation of biology.
They studied a wide range of compounds that may have formed as a result of prebiotic reactions in the early Earth.
And they found that many of these substances are ethers,amines, azides, imides and others - under certain conditions polymerize more easily than biological compounds. And some even spontaneously create cell-like structures - compartments. According to the authors, the chains of polymers inside such compartments, twisting, could form unique three-dimensional forms - prototypes of proteins or RNA.
For obtaining polymer chains in the laboratorythe authors used periodic alternation of dry and wet conditions. Evaporation of the dilute solution, as a rule, started the polymerization process, but not all of the formed polymers withstood drying. Some fell apart. Others, with the addition of water, continued the self-replicating synthesis cycle. In this, the authors see the earliest, even at the level of molecules, a manifestation of evolutionary selection, which later became an integral feature of all living organisms.
The researchers examined the polymers under a microscope andfound that inside some of them cell-sized compartments appeared: they contained from 10 to 20 atoms. According to scientists, over time, these cell-like aggregates, after long chemical transformations, could become full-fledged cells - self-organizing structures consisting of millions atoms.
What was important for the birth of the first cells?
The conditions in the pond that Darwin spoke of werethe basis for the origin of life, this has been confirmed by research. The peculiarity of the abstract pond is that it sometimes it becomes filled with water, sometimes it dries out. That is, the cyclic alternation of wet and dry periods contributes to the appearance of complex prebiotic compounds in the chemical system, as physicists also confirm.
The authors investigated polyelectrolyte coacervates inliquid medium having the same composition as the water in the pond. They simulated conditions where the pond dries up and then refills with rainwater. And they found out: in the first case, the concentration of nucleic acids and salts increases, in the second it decreases. It does not change inside the polymer compartments.
According to the researchers, this has become a key factor in the gradual formation of complex self-reproducing polymeric compounds, such as RNA, inside protocells.
Accordingly, three conditions are needed for life:
- compartmentalization,
- self-replication,
- metabolism.
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