The theory of abiotic synthesis: what it is and what questions it attempts to answer

A summary of the theory of abiotic synthesis and the questions about life on which it focuses.

Understanding the origin of life is, for human beings, one of the most complex and mystical questions that can be proposed. How did the cell, the basic unit of living things, arise from inert compounds? What is the underlying motive that led to the emergence of living things from the elements that make them up?

The simple concept of "non-life" is enormously complex to understand because, on a planet with more than 8.7 million estimated species (most of them undiscovered), the simple fact of conceiving the lack of sentient organic matter at some point in Earth's history is, without a doubt, a challenge for even the best of scientists.

Here we will explore a topic that goes beyond the very existence of human beings, as we try to elucidate the hypotheses and assumptions that have tried to explain the origin of life on our planet. It is the field of abiogenesis and the theory of abiotic synthesis, where we try to explain the existence of life on our planet.where it is tried to explain the existence of being from nothing.

What is the theory of abiotic synthesis?

Abiogenesis refers to the natural process of emergence of life from the non-existence of this, that is to say, on the basis of inert matter, simple organic compounds.simple organic compounds. The scientific community estimates that the origin of life dates from a period between 4.41 billion years ago, when water vapor began to condense regularly on Earth, and 3.77 billion years ago, when the first signs of life were found.

The "classical" theory on the origin of life involves some insurmountable logistical drawbacks, which have been covered in scientific review articles in multiple instances. To understand the complexity of elucidating this process, here are some of them:

• These postulations obscure the very concept of "life". There is no reducible conclusion concerning the self-synthesis of living forms in space-time.
• The production of the first living things is placed in the primitive seas, whose conditions were too aggressive for any kind of life to thrive.
• He states that protobionts "received" life by the simple fact of acquiring a complex molecular structure.
• For something to be alive, DNA is required, a fact almost inconceivable in a climatically arduous environment such as the primitive seas.
• Which came first, the chicken or the egg? That is, how did the first living things replicate if we assume that they did not have DNA or RNA?

It is time to get a little metaphysical, because the third point on this list is particularly striking. Not even by ordering all the substances required to give rise to the simplest cell type of all, have we managed to obtain a structure that experiences life, which is why the "living being" is a "living being".The abiotic synthesis from abiotic synthesis to abiotic synthesis from abiotic synthesis must be more than the sum of all its parts, must it not?

Abiotic synthesis from organic molecules: Miller's experiment

The theory of abiotic synthesis could not be conceived today without the Miller experiment, which was carried out in 1953 by Stanley Miller and Harold Clayton Urey (biologist and chemist) at the University of Chicago. To try to explain the origin of life in a laboratory environment, these experts needed a series of glass containers and tubes connected to each other in a closed circuit..

In general terms, we can summarize the experiment as follows: a mixture of water, methane, ammonia, carbon dioxide, nitrogen and hydrogen (the compounds possibly present at the time of the origin of life) was mixed and subjected to electrical discharges of 60,000 volts at very high temperatures.

From these elements, from the energy supplied to the system and from the interconnected glass tubes, various glass molecules were obtained. various molecules of an organic nature were obtained, including glucose and some amino acids.. These compounds are essential for protein synthesis by cells, i.e. the basis of their growth and development.

After this incredible experiment, several variants of the procedure have been performed in laboratory environments. Thanks to trial and error, the following milestones have been achieved:

• 17 of the 20 amino acids that make up proteins have been formed from inorganic compounds.
• All the purine and pyrimidine bases that allow the creation of nucleotides, which associate to form DNA and RNA in the cell, have been synthesized.
• One study claims to have created nucleotides from pyrimidine bases, although this process is much more difficult to achieve.
• Nine of the 11 intermediates of the Krebs cycle have been created.

Despite all these advances, explaining the formation of organic matter from inorganic matter remains a puzzle.. For example, it is theorized that, at the time of the origin of life, the concentration of methane and ammonia in the atmosphere was not high, which is why the experiment we have presented loses a little strength. Moreover, explaining the origin of organic molecules is the first step to understand the emergence of life, but as we have seen, an association of molecules requires something "special" to be conceived as life.

Hypothesis of the origin of life

For a hypothesis to answer the origin of life, it must solve the following doubts:

• How the essential molecules that define life, i.e. amino acids and nucleotides, were created (the experiment previously described may give a partial answer).
• How these compounds were associated to give rise to macromolecules, i.e. DNA, RNA and proteins (a much more difficult process to explain).
• How these macromolecules were able to self-reproduce themselves (no answer).
• How these macromolecules were delimited into autonomous forms separate from the medium, i.e., the cell.

Perhaps Miller's experiment and its variants cover, to some extent, the first two questions. Even so, explaining the rest of the unknowns is a titanic task. In 2016, a study in the journal Nature managed to go a step further with regard to this issue: they studied the physics of small "active droplets", formed by the segregation of molecules in complex mixtures resulting from phase changes..... In other words, they were chemically active droplets that recycled chemical components in and out of the surrounding liquid.

What is fascinating about this study is that the practitioners found that these droplets tended to grow to cell size and, to some extent, divide by similar processes. This could provide a clear model for the "prebiotic protocell," ie, the existence of compartmentalized entities in which chemical processes take place even though they are not alive per se.. Of course, we are moving in areas that are difficult to understand, but the general idea is the following: scientific advances are being made that try to give answers to the postulated questions.

Other hypotheses

Abiogenesis on Earth, or, in other words, the theory of abiotic synthesis (creation of life from organic matter), are not the only hypotheses being considered. are not the only hypotheses that have been put forward to explain life on our planet.. The clear example of this is panspermia, a completely different current that tries to explain the arrival of the first microorganisms on Earth by means of exogenous bodies, i.e. meteorites.

Multiple discoveries have been made on this subject, since some bacterial colonies have shown resistance to space conditions.The first stage, the exit from orbit of a planet and the subsequent entry. Even so, it has not been possible to prove survival in all 3 stages at the same time and, once again, we are faced with laboratory conditions.

Hypotheses such as panspermia are also a problem in themselves, since they try to explain how life arrived on earth, but not its real origin. For this reason, the fact that an association of organic molecules gave rise to life remains, to this day, a real unknown.

Summary

As we have seen, since Miller's experiment, enormous advances have been made in the theory of abiotic synthesis: from the synthesis of almost all amino acids to the nucleotide, we have almost succeeded in creating "all" the elements necessary from inorganic matter for a cell to start up.

Unfortunately, the question remains: how did these molecules come together to form the cell? Research such as that described above and published in the journal Nature attempts to answer this question by studying non-living "proto-cells" composed of organic molecules that react with the environment in a manner similar to that of a cellular entity. Of course, the road ahead is long and the question of the origin of life is still valid.

Bibliographical references:

• Abiogenesis, The origin of life on Earth, Nasif Nahle Sabag, Omegalfa Library.
• Ménez, B., Pisapia, C., Andreani, M., Jamme, F., Vanbellingen, Q. P., Brunelle, A., ... & Réfrégiers, M. (2018). Abiotic synthesis of amino acids in the recesses of the oceanic lithosphere. Nature, 564(7734), 59-63.
• Zwicker, D., Seyboldt, R., Weber, C. A., Hyman, A. A., & Jülicher, F. (2017). Growth and division of active droplets provides a model for protocells. Nature Physics, 13(4), 408-413.