Primordial molecule

None of this precludes the existence of special mechanisms for initiating glycan chains in the absence of existing peptidoglycan. In reality bacteria will normally have some peptidoglycan, or similar protein, in their walls and there will never be an obvious necessity of them to produce it de novo but there remains the theoretical problem of the origin of the primordial molecule. 

The nucleotides which consist of three parts, namely a nitrogenous base, a pentose sugar and a phosphate radical, are a very important group of compounds since one or more of them is involved in virtually every biochemical process. The adenosine di- and tri-phosphates which play an essential part in cellular energy exchanges have a nucleotide-type structure as do many of the coenzymes. Furthermore, nucleotides constitute the monomeric units of which the nucleic acids are composed that is to say nucleic acids are polynucleotides. The nucleic acids which are of two types, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), are responsible for directing the synthesis of proteins. They specify the unique sequence of amino acids in any particular protein and consequently should be regarded as primordial molecules on whose existence that of the proteins depends. However, since the synthesis of the nucleic acids depends on enzymes which are themselves proteins, this poses the fundamental evolutionary question as to which came first - the biochemical version of the problem of the chicken and the egg ... 

The prebiotic primeval soup, i.e., the oft-cited mixture of organic molecules in the primordial ocean, or in ponds which could have arisen in many ways, e.g., in the atmosphere or the hydrosphere the substances concerned could also have been delivered from outer space. 

Extraterrestrial origins of life Terrestrial origins of life Life was delivered to the Earth (or any planet) by meteorites of cometary material, leading to the idea of panspermia The molecules of life were built on Earth, perhaps in the primordial soup or little warm pool... 

The pH of the oceans forming the primordial soup is important in controlling the charged nature, or otherwise, of the amino and carboxylic acid species and hence their chemistry. Generating reaction schemes for the prebiotic synthesis of molecules requiring basic conditions will not be relevant if the oceans are acidic. Consider dissolving CO2 into water, simply written as ... 

Changing the initial conditions in the Urey-Miller experiment to favour a primordial atmosphere with CO2 as the primary carbon source does not produce such a rich mixture of prebiotic molecules and there is a significantly lower yield of amino acids an argument against an endogenous source of organic molecules. 

The opportunities for concentrating and detecting (probably primordial) quarks and the properties of adducts of atoms, ions and molecules with quarks are discussed. There is a pronounced difference between positive quarks located in the outer valence-regions (or in the conduction electrons of metals) and negative quarks so firmly bound to nuclei that they may not be mobile, and constitute a kind of new elements with (Z - 1/3). Analogies are drawn with neutrinos, muons and other well-established particles. 

Isaac Beeckman (1588-1637 CE), a Dutch natural philosopher, proposed a molecular theory in his scientific diary . He assrrmed that there were four kinds of atoms corresponding to the four elements of the one sole primordial matter. He considered these atoms to be the cause of the properties of the substances, for example, color, taste, smell, etc. The molecules of substances were called homogenea physica (physical homogenea) and were composed of the atoms in specific spatial stracture. His private diary was available to several savants such as Descartes, who acknowledged these ideas in several books (41). 

Some time after the evolution of this primitive protein-synthesizing system, there was a further development DNA molecules with sequences complementary to the self-replicating RNA molecules took over the function of conserving the genetic information, and RNA molecules evolved to play roles in protein synthesis. (We explain in Chapter 8 why DNA is a more stable molecule than RNA and thus a better repository of inheritable information.) Proteins proved to be versatile catalysts and, over time, took over that function. Lipidlike compounds in the primordial soup formed relatively impermeable layers around self-replicating collections of molecules. The concentration of proteins and nucleic acids within these lipid enclosures favored the molecular interactions required in self-replication. 

Very primitive multicellular organisms, such as the hydra (e.g., Chlorohydra viriiissima, the ultimate simple feeding tube), have nervous systems that may only use simple proteins as neurotransmitters, suggesting that these proteins were the first signaling molecules used by primordial nervous systems. If we extract a few of these proteins from the brain of a typical Hydra and inject them in human neurons, they will actually produce similar signaling responses from those neurons. 

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