Theoretical origin of life; mimicking the Krebs cycle (Introduction)

by David Turell , Monday, March 13, 2017, 17:41 (2593 days ago) @ David Turell

A part of the ubiquitous mechanism in life supplying energy is the Krebs cycle, a circular arrangement of organic molecules. This lab experiment using many thousand trials finds a sulpher based mimic as a theoretical start of life. It is just fun and games for chance to do this. It is also touted to be enzyme-free which makes it easier to form:

https://phys.org/news/2017-03-enzyme-free-krebs-key-life-earth.html

"The researchers have demonstrated a network of chemical reactions in the lab which mimic the important Krebs cycle present in living organisms today. In a study published in the journal Nature Ecology and Evolution, they say it could explain an important step in how life developed on Earth.

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"The research group from the Francis Crick Institute and the University of Cambridge say their demonstration offers an answer. They have shown an enzyme-free metabolic pathway that mirrors the Krebs cycle. It is sparked by particles called sulphate radicals under conditions similar to those on Earth four billion years ago.

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"The scientists used simple carbon compounds which are involved at various points in the Krebs cycle (such compounds have recently been found in a meteorite by NASA scientists) and mixed them with iron and sulphur-containing chemicals that would be found in sediments in the early oceans.

"We took components representative of the sediments present on Earth billions of years ago." says Dr Ralser, "As salts that would have been present in the sediments did not trigger many reactions, we mostly concentrated on metal ions and sulphate species. These are also known to be important in the modern cell's Krebs cycle.

""We conducted a huge screen involving thousands of measurements then systematically worked through them. At the end we found a condition that may have enabled the Krebs cycle to emerge. It relies on sulphate radicals and previously nobody had thought about them." (my bold)

"An alternative hypothesis for the origin of life suggests that RNA - a molecule similar to DNA that can maintain genetic information but is more transient and more reactive - can explain the first steps towards life. This is known as the RNA-world hypothesis.

"Dr Ralser says: "There is a huge scientific debate about whether the first steps towards life were driven by metabolism or genetics."

"He argues that the presence of RNA molecules cannot easily explain the origin of metabolism, as RNA is made from products of metabolism. And that his group's results support the theory that environmental chemistry enabled metabolism to begin.

"'People have tried to work on a non-enzymatic Krebs cycle for years, but most have thought about it theoretically or philosophically. Few have done systematic physical experiments like those we report here. A non-enzymatic catalyst for the Krebs cycle exists and we have found it," concludes Dr Ralser."

Comment: More fun and games in the lab resulting in intelligent design of a system that is unlikely to form by chance. See my bolded area.