LA TAVOLA DELLA VITA

THE TABLE OF LIFE

The periodic table contains all the elements of life, although some of them still act in mysterious ways in our bodies. Under certain conditions, a usually toxic element can turn out to be a life-saving drug, and elements metabolized in unexpected ways can provide doctors with new diagnostic tools. The elements of the periodic table, in their simplest form as atoms, combine to form molecules, which are formed by two or more atoms, equal or different, bonded together. When chemical elements react together to form a new chemical compound, the properties of the product of the reaction are not necessarily the same as those of the starting elements.

These molecules are also part of our body and are assimilated to provide us with energy and nutrients. This process of assimilation is called metabolism. Metabolism is a process by which a molecule is modified or destroyed by the body, and this has four main and specific functions: to derive chemical energy from the breakdown of energy-rich nutrients; to convert nutrient molecules into the basic precursors of cellular macromolecules; to utilize these basic precursors to form proteins, nucleic acids, lipids, polysaccharides, and other substances; and to form and degrade biomolecules necessary for specialized functions of cells. Our body, in practice, is an elaborate chemical laboratory!

Thanks to the interaction between chemistry, the study of the elements and medicine, and the study of the human body and drugs, one can even understand how life emerged from the elements of the periodic table.

Famous is the experiment of Miller and Urey, who demonstrated that it is possible to obtain various organic molecules, i.e. those carbon-containing molecules found in living beings, including some amino acids. They succeeded in demonstrating this in the presence of electric discharges, a simulation of lightning, with water and a mixture of gases, including methane and ammonia, thus recreating the habitat where life probably developed on our planet.

Amino acids are organic compounds containing a carboxyl group (COOH) and an amine group (NH2 ). In addition to these two groups, each amino acid is distinguished from the others by the presence of a residue (R) also known as the amino acid side chain. Amino acids are essential to life: 12 types can be synthesized by the body, 8 must be taken in with food, and are therefore called essential.

Recent studies by a team of NASA researchers, led by astrobiologist Laurie Barge, have recreated this primordial soup, even going so far as to simulate the conditions of marine abysses near hydrothermal vents where the sun’s rays do not penetrate. This broth is a mixture of water, ammonia molecules, and pyruvate, a sugar with three carbon atoms, elements considered essential for the emergence of life that are normally found near hydrothermal vents.

By bringing this mixture to 70°C and reducing the oxygen present, important molecules such as alanine (an amino acid responsible for the synthesis of many proteins) and lactate, the chemical compound that some scientists believe is the agent that allows life to thrive, were subsequently detected. The NASA team did not recreate life from scratch but simply demonstrated that the fundamental elements at the origin of life are present near hydrothermal vents and that therefore the presence of such fractures on the surface of other planets (such as exoplanets, i.e. planets outside the Solar System) could indicate the presence of extraterrestrial life.