Theoretical origin of life; more lab play (Introduction)

by David Turell , Wednesday, July 25, 2018, 21:42 (2102 days ago) @ David Turell

this time the lab work proposes lots of fatty substances were on Earth to fascilitate the joining together of organic compounds:

https://phys.org/news/2018-07-century-old-life-significant-substantiation.html

"In 1924, Russian biochemist Alexander Oparin claimed that life on Earth developed through gradual chemical changes of organic molecules, in the "primordial soup" which likely existed on Earth four billion years ago. In his view, the complex combination of lifeless molecules, joining forces within small oily droplets, could assume life faculties—self-replication, selection and evolution. These ideas were received with considerable doubt, still pertaining today.

"Thirty years later, when DNA structure was deciphered, it was realized that this molecule is capable of self-replication, seemingly solving the enigma of life's origin without resort to Oparin's droplets. But critics argued that life requires not only replicators, but also enzyme catalysts to control­ metabolism. Another 30 years passed before the discovery that RNA, key component in information transfer from DNA to proteins, can also be an enzyme. This is how the concept of "RNA World" was born, whereby life began when the primordial soup gave birth to a ribozyme, which can both replicate and control metabolism.

"Despite this doubts lingered, because a replicating ribosome is a highly complex molecule, with negligible probability of spontaneous appearance in the soup. This led to an alternative concept—mutually catalytic networks, affording the copying of entire molecular ensembles.

"This idea echoes Oparin's evolving complex combination of simple molecules, each with high likelihood of appearance in the soup. What remained was to generate a detailed chemical model that will help support such a narrative.

"Prof. Doron Lancet and colleagues at the Weizmann Institute of Science, Dept. of Molecular Genetics came up with such a model. First, it was necessary to identify the appropriate type of molecules, that can accrete together and effectively form networks of mutual interactions, in line with Oparin's droplets. Lancet proposed lipids, oily compounds that spontaneously form the aggregated membranes enclosing all living cells. Lipid bubbles (vesicles) can grow and split much like living cells. This is how Lancet generated the concept "Lipid World" two decades ago.

***

"Based on the computer model they developed, the scientists demonstrated that specific lipid compositions, called "composomes", can undergo compositional mutations, be subject to natural selection in response to environmental changes, and even undergo Darwinian selection. Prof. Lancet comments that such an information system, which is based on compositions and not on the sequence of chemical "letters" as in DNA, is reminiscent of the realm of epigenetics, where traits are inherited independent of the DNA sequence. This lends credence to the scientists' assumption that life could emerge before the advent of DNA and RNA. In their article they in fact delineate a chemical path that lead to the appearance of genetic material in the framework of the oily droplets.

"Lancet's "Lipid World" concept is contingent upon the question of whether there were sufficient oil-like "water hating" molecules in the primordial soup. Here too, the scientists describe a comprehensive literature search, according to which there is a high probability for such molecules to be present on early Earth."

Comment: As usual full of hope with no real substance to the hope that lipids were all over the Earth at the beginning of first life or even in some lucky spots. I don't know that meteorites showed lipids when analyzed. The Murchison meteorite did not.