Theoretical origin of life: possible early beginning (Introduction)

by David Turell , Monday, October 12, 2020, 19:28 (1290 days ago) @ David Turell

Using two common amino acids and a little heat and early parts of the Krebs (TCA) molecular energy supplying cycle can form naturally:

https://www.quantamagazine.org/new-clues-to-chemical-origins-of-metabolism-at-dawn-of-l...

"A central pillar of all cellular metabolism — and the bane of generations of high school biology students who had to memorize it — is a complex 10-step chemical process variously known as the tricarboxylic acid (TCA) cycle, the citric acid cycle or the Krebs cycle. “The TCA cycle is at the heart of much of modern biology, where it is used both to break down food into energy and to synthesize vital building blocks of proteins,” said Greg Springsteen,

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"Because the TCA cycle feeds into so many vital processes in even the simplest cells, scientists suspect it was one of the early reactions to establish itself in the prebiotic soup.

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"They started with just two compounds — glyoxylate and pyruvate, the two smallest alpha-ketoacids, containing only two and three carbon atoms respectively. Alpha-ketoacids drew their attention because of “their stability in water and their propensity to form carbon-carbon bonds, the skeleton of biology,” Springsteen said.

"Astonishingly, they found that the glyoxylate and pyruvate reacted to make a range of compounds that included chemical analogues to all the intermediary products in the TCA cycle except for citric acid. Moreover, these products all formed in water within a single reaction vessel, at temperatures and pH conditions mild enough to be compatible with conditions on Earth.

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"Krishnamurthy and Springsteen both emphasize that their experiments do not prove that the ancestor of the TCA cycle emerged this way: There are similarities between the reactions and intermediary molecules they created and those in the TCA cycle, but without further evidence, it is more prudent to refer to them as analogs of TCA cycle intermediaries. They did not create a cycle of any kind, just a mixture of molecules that could in principle be organized to act as one.

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"But if the precursors of cells had those molecules at their disposal, then they might have performed some of the synthetic chemistry useful to life. That first draft of metabolism would almost certainly have been crude and poorly controlled, and it might not have even been organized into a complete cycle. But over time, as proteins also became part of the mix, enzymes could have taken control over some of the reactions, and the real TCA cycle might have started to take shape. " (my bold)

Comment: The bold above shows all the caveats, while pursuing wishful thinking. Where do the required giant enzymes come from? Where the original molecules used in this study present on
Earth at that time? But a good try.