Building blocks of life

Oxygen is the most abundant element on earth The earths crust is rich in carbonate and sili cate rocks the oceans are almost entirely water and oxygen constitutes almost one fifth of the air we breathe Carbon ranks only fourteenth among the elements in natural abundance but trails only hydro gen and oxygen in its abundance in the human body It IS the chemical properties of carbon that make it uniquely suitable as the raw material forthe building blocks of life Let s find out more about those chemi cal properties... 

Weinkauf R, Schermann JP, de Vries MS, Kleinermanns K (2002) Molecular physics of building blocks of life under isolated or defined conditions. Eur Phys J D 20 309... 

Formation of the building blocks of life. In Life s Origin, The Beginning of Biological Evolution, ed. J. W. Schopf. California University Press, pp. 100-9. 

However, despite its apparently fundamental role in creating the building blocks of life, electricity has not become one of the foremost means of manipulating organic molecules to useful end.84 Nevertheless, where it can be applied to remove or add electrons in specific ways, electricity offers unique and often advantageous approaches to carrying out oxidation and reduction reactions. The interested reader is referred to several of the books published on the subject for further education.85... 

Carbonaceous chondrites are rare stony meteorites that contain complex carbon compounds from which they get their name. Some contain water and amino acids, the building blocks of life. Carbonaceous chondrites are believed to be samples of our solar system s earliest rocks, unchanged after nearly 4.6 billion years. 

Approximately 1 billion years after Earth s formation, life appeared, as already mentioned. Before life could exist, though, another major process needed to have taken place—the synthesis of the organic molecules required for living systems from simpler molecules found in the environment. The components of nucleic acids and proteins are relatively complex organic molecules, and one might expect that only sophisticated synthetic routes could produce them. However, this requirement appears not to have been the case. How did the building blocks of life come to be ... 

In exploring the origins of life, we are faced with one of two possibilities either the molecules of life were assembled on Earth or the building blocks of life were formed as part of the more general astrochemistry that gave birth to the solar system. The former leads to a more "Earth Centric" view ofthe universe suggesting that the Earth fulfilled some rather special criteria to allow molecules to assemble while the latter is more conducive to life being a universal phenomenon equally probable in any other solar system. 

The suggestion that the molecular building blocks of life could be formed in space is intriguing since such regions would seem to be rather unlikely places for the development of chemistry. The ISM is cold (temperatures of 10-30 K) and "empty" with pressures of less than 10 2 torr such that the probability for a collision between two compounds is low and, at such low temperatures, the "reaction rate" would be expected to be very low (hence in most industrial chemistry the reactants are heated to increase their reactivity). Nevertheless the detection of such molecules within the ISM makes it clear that these are chemically active zones. The solution to this apparent paradox is that the chemistry in the ISM is somewhat different from the conventional chemistry we observe on Earth, much of it being induced by radiation. The ISM contains several different sources of radiation, namely ... 

Demonstrating that it is possible to form molecules in the ISM that may subsequently assemble to form the building blocks of life on Earth (or any other planet) is not in itself evidence that the origins of life lie in the ISM. It is also necessary to know how such molecules might be transported to the planet. Our knowledge of how stars and planets form relies on physical/chemical models but we believe we know the basic mechanisms. Within the ISM... 

It is generally accepted that products of cosmic chemistry were showered on the nascent earth and could likewise fall on many other celestial bodies, brought down by comets, meteorites, and cosmic dust. But there is no agreement on the contribution of such products to the origin of life. Some researchers believe that the bulk of the building blocks of life came from outer space, others that they arose in the primitive terrestrial atmosphere by the kinds of process Miller and others have tried to reproduce in the laboratory. Most likely, both sources contributed, but in proportions that remain to be evaluated. 

Life as we know it today completely depends on water. Without water, life would be either impossible or totally different. Thus, a deep understanding of the relationship between water and other simple building blocks of life is crucial to gain insight into how prebiotic life forms could have originated and evolved and whether the physical laws of this universe are in any way predisposed to the emergence of life (Henderson, 1913, 1917 Eisenberg and Kauzmann, 1985 Ball, 2001). 

It is unlikely that under prebiotic conditions the complex and sophisticated biomacromolecules commonplace in modem biochemistry would have existed. Thus, research into the origin of life is intimately associated with the search for plausible systems that are much simpler than those we see today. However, it is also plausible that these simple building blocks of life might have been amphiphilic molecules in which water could have had an enormous influence on their prebiotic molecular selection and evolution, because water can either form clathrate stmctures or drive these simplest molecules together (Ball, 2001). 

Fries, K, and S. I. O Donoghue. 2002. Navigating around the building blocks of life. Advanced Imaging 17 18-9, 39. 

Four billion years ago the molecular building blocks of life had been synthesized, and these molecules must have become locally concentrated on surfaces and through self-selection as they assembled into vesicles and polymers of biological interest. Yet accumulations of organic molecules, no matter how highly selected and intricately organized, are not alive unless they also possess the ability to reproduce. 

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