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

Understanding the origin of life is, for the human being, one of the most complex and mystical issues that can be proposed. How did the cell, the basic unit of living things, arise from nonliving compounds? What is the underlying reason that led to the appearance of living beings 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 without discover), the simple fact of conceiving the lack of sentient organic matter at some point in the history of the Earth is, without a doubt, a challenge even for the best of humans. scientists.

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

• Related article: "Top 10 theories of the origin of life"

What is the theory of abiotic synthesis?

Abiogenesis refers to the natural process of emergence of life from its non-existence, that is, based on inert matter, simple organic compounds. The scientific community estimates that the origin of life dates from a period between 4,410 million years old, when the steam of water began to condense regularly on Earth, and 3,770 million years ago, moments in which the first signs of life.

The “classical” theory of the origin of life involves some insurmountable logistical drawbacks, which have been covered in scientific review articles. in multiple instances. To understand the complexity when elucidating this process, we present some of them:

• These postulations obscure the very concept of “life”. There is no reducible conclusion regarding the self-synthesis of living forms in space-time.
• The production of the first living beings is located in the primitive seas, whose conditions were too aggressive for any type of life to thrive.
• It establishes that the 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 an environment as climatically harsh as the primitive seas.
• What was the first; the egg or the chicken? That is, how did the first living beings replicate if we assume that they did not have DNA or RNA?

It's time to get a little metaphysical, because the third point on this list especially calls our attention. Not even 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, reason for which the "being" must constitute something more than the sum of all its parts, right?

Abiotic synthesis from organic molecules: Miller's experiment

The theory of abiotic synthesis could not be conceived today without Miller's 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 together in a closed circuit.

In general lines, we can summarize the experiment in the following concepts: a mixture of water, methane, ammonia, carbon dioxide, nitrogen and hydrogen (the compounds possibly present at the time of the origin of life) and this was subjected to electrical discharges of 60,000 volts at very tall.

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

After this incredible experiment, various variants of the procedure have been carried out in laboratory settings. Thanks to trial and error trials, the following milestones have been achieved:

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

Despite all these advances, explaining the formation of organic matter from inorganic 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 that we have exposed to you loses a bit of force. In addition, explaining the origin of organic molecules is the first step to understand the emergence of the life, but as we have seen, an association of molecules requires something "special" to be conceived as life.

• You may be interested in: "The theory of biological evolution: what it is and what it explains"

Origin of life hypothesis

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

• How the essential molecules that define life, that is, amino acids and nucleotides, were created (the experiment described previously can give a partial answer).
• How these compounds were associated to give rise to macromolecules, that is, DNA, RNA and proteins (much more difficult process of explanation).
• How were these macromolecules able to self-reproduce themselves (no answer).
• How these macromolecules were delimited in autonomous forms separated from the environment, that is, 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 daunting task. In 2016, a study in the journal Nature managed to go one step further in relation to this issue: 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's fascinating about this study is that the practitioners found that these droplets tended to grow to the size of a cell and, to some extent, divided by similar processes. This could suppose a clear model for the "prebiotic protocell", that is, the existence of compartmentalized entities in which chemical processes occur despite the fact that they were not alive per se. Of course, we are moving in areas that are difficult to understand, but the general idea is the next: scientific advances are being made that try to answer the questions postulates.

Other hypotheses

Abiogenesis on Earth, or what is the same, the theory of abiotic synthesis (creation of life from organic matter) They are not the only hypotheses considered to explain life on our planet. The clear example of this is the panspermia, a completely different current that tries to explain the arrival of the first microorganisms on Earth through exogenous bodies, that is, meteorites.

Many discoveries have been made regarding this subject, since some bacterial colonies have shown resistance to space conditions, the departure from orbit of a planet and the subsequent entrance. Even so, it has not been possible to verify survival in the 3 stages at the same time and, once again, we are dealing with laboratory conditions.

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

Summary

As we have been able to see, since Miller's experiment enormous advances have been made in terms of the theory of abiotic synthesis: from the synthesis of almost all the amino acids up to the nucleotide, they have almost managed to create "all" the necessary elements from inorganic matter for a cell to put itself into March.

Unfortunately, the question remains: how did these molecules associate to give rise to the cell? Research such as the one previously described and published in the journal Nature try to answer this question, through the study of non-living "proto-cells" composed of organic molecules that react with the environment in a similar way to an entity cell phone. Of course, there is a long way to go and the question of the origin of life remains valid.

Bibliographic references:

• Abiogenesis, The origin of life on Earth, Nasif Nahle Sabag, Omegalfa Library.
• Menez, 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., & Julicher, F. (2017). Growth and division of active droplets provides a model for protocells. Nature Physics, 13(4), 408-413.