phosphorus
HURDLE NUMBER 12. THE PHOSPHORUS HURDLE.
RNA and DNA are composed of nucleotides. Nucleotides are composed of a base + a sugar (ribose) + a phosphate group. The problem is that the primordial soup would NOT HAVE CONTAINED ANY PHOSPHORUS to make the phosphate group. Here are some quotes from authoritative sources which substantiate this statement:-
This quote is from the book How Life Began by L.R. Croft, Lecturer in Biological Sciences at The University of Salford, published by Evangelical Press, 1988, page 49:-
“Nucleic acids (ie:- RNA and DNA) are formed when nucleotides polymerize (ie:- join together into long chains of molecules) - - - - Nucleotides - - - - consist of a base + sugar (ribose) + phosphate. The first problem regarding their prebiotic formation is the origin of the phosphate. In watery environments the predominant form of phosphorus is phosphoric acid - - - -However, on the primeval earth this would combine with calcium and other alkaline earth metals, so that there would be very little dissolved phosphate in the primordial soup.”
The next quote is from the book The Origins of Life On The Earth by Stanley L. Miller (of The University of California, San Diego) and Leslie Orgel (of The Salk Institute, California), published by Prentice Hall, 1974, page 130:-
The authors tell us that the phosphorylation (ie:- joining a phosphate group to another molecule) of nucleoside can be achieved by heating them with ACID phosphates (My capitals). They then point out an important problem:- “It seems unlikely that the pH (ie:- the acidity/alkalinity measure) of - - - - - oceans or - - - - - lakes on the primitive earth could ever have been low enough (ie:- acidic enough) to permit the formation of acid salts of phosphoric acid - - - - - Neutral or alkaline salts (ie:- of phosphorus) - - - - do not take part in the phosphorylation reaction.”
The next quote is from the book The Origin of Life and Evolutionary Biochemistry, edited by K Dose (Inst. Fur Biochemie, Univeritat Mainz, Germany) and S.W. Fox (Inst for Molecular and Cellular Evolution, University of Miami, Florida) et al, published by Plenum Press, NY and London, 1974. The article in this book that I am quoting from is An Evolutionary Model for Prebiotic Phosphorylation by Alan W. Schwartz (Dept. of Exobiology – University of Nijmegen, Netherlands:-
“Clearly - - - more work is necessary before any definitive model can be proposed to account for the sources of phosphorus on the primitive earth - - - - - The only source of phosphorus now known to exist to any extent on the surface e of the earth - - - - is apatite (a mineral) - - - - all of the known forms of apatite are highly insoluble in neutral and basic solution, and slightly soluble in - - - -weak acids.”
(My comment:- As we have seen in the previous quote, the primeval soup, either in ocean or lake, would NOT have been acidic enough to dissolve the apatite, and make available the phosphorus to make the nucleotides for RNA and DNA.)
The next quote is from the same book:- Article:- Evolution and Ecology of Phosphorus Metabolism by M. Halmann – Isotope Department –Weizmann Institute of Science, Rehovot, Israel:-
“The problem of concentration is - - - serious - - - -The concentration of phosphorus - - - - in ocean or freshwater - - - is - - - - usually in the range of about 10 – 7 M - - - - - - Attempts to create - - - phosphorylation using such low concentration of phosphate have not been successful.”
The next quote is from the book – Quantitative Chemical Analysis – by A.C. Cumming, D.Sc. and S.A. Key, D.Sc. , published by Gurney and Jackson, 1948, page 490:-