Theoretical origin of life: just one step!!! (Introduction)

by David Turell , Friday, January 26, 2024, 01:13 (92 days ago) @ David Turell

Another nutty review article with a new twist:

https://www.newscientist.com/article/mg24732940-800-a-radical-new-theory-rewrites-the-s...

"Many ideas have been proposed to explain how life began. Most are based on the assumption that cells are too complex to have formed all at once, so life must have started with just one component that survived and somehow created the others around it. When put into practice in the lab, however, these ideas don’t produce anything particularly lifelike. It is, some researchers are starting to realise, like trying to build a car by making a chassis and hoping wheels and an engine will spontaneously appear.

"The alternative – that life emerged fully formed – seems even more unlikely. Yet perhaps astoundingly, two lines of evidence are converging to suggest that this is exactly what happened. It turns out that all the key molecules of life can form from the same simple carbon-based chemistry. What’s more, they easily combine to make startlingly lifelike “protocells”. As well as explaining how life began, this “everything-first” idea of life’s origins also has implications for where it got started – and the most likely locations for extraterrestrial life, too.

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"Life can be boiled down to three core systems. First, it has structural integrity: that means each cell has an outer membrane holding it together. Second, life has metabolism, a set of chemical reactions that obtain energy from its surroundings. Finally, life can reproduce using genes, which contain instructions for building cells and are passed on to offspring.

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"Beyond this, things start to become more complicated. Life’s three core processes are intertwined. Genes carry instructions for making proteins, which means proteins only exist because of genes. But proteins are also essential for maintaining and copying genes, so genes only exist because of proteins. And proteins – made by genes – are crucial for constructing the lipids for membranes. Any hypothesis explaining life’s origin must take account of this. Yet, if we suppose that genes, metabolism and membranes were unlikely to have arisen simultaneously, that means one of them must have come first and “invented” the others.

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"...biochemists have spent decades struggling to get RNA to self-assemble or copy itself in the lab, and now concede that it needs a lot of help to do either.

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"In the 1970s, his team discovered that lipids found in cell membranes could be made when two simple chemicals, cyanamide and glycerol, were mixed with water and heated to 65°C. If these lipids were subsequently added to salt water and shaken, they formed spherical blobs with two outer layers of lipids, just like cells. “The simplest function is the self-assembly of membranes. It’s spontaneous,” says Deamer. Nevertheless, he now accepts that this isn’t enough, because lipids can’t carry genes or form enzymes.

"The shortcomings of these simple models of life’s origin have led Deamer and others to explore the seemingly less plausible alternative that all three systems emerged together in a highly simplified form.

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"In 2001, his team found that formamide could give rise to several components of RNA if it was heated to 160°C in the presence of minerals like limestone. The researchers later discovered that a common type of clay called montmorillonite helps. Formamide can also generate amino acids, the building blocks of proteins. “It produces complex mixtures,” says Di Mauro.

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"By combining a similar organic compound called cyanamide with other simple chemicals, John Sutherland at the MRC Laboratory of Molecular Biology in Cambridge, UK, has created nucleotides, the building blocks of RNA. The reaction requires ultraviolet light, heating and drying, and wetting with water. Sutherland’s team found that the same starting chemicals can also make the precursors of amino acids and lipids. “All the cellular subsystems could have arisen simultaneously through common chemistry,” he concluded. The key is what Sutherland calls “Goldilocks chemistry”: a mixture with enough variety for complex reactions to occur, but not so much that it becomes a jumbled mess. (my bold)

"Jack Szostak at Harvard Medical School has taken remarkable strides toward revealing how this might have happened. Beginning in 2003, his team built model cells with outer layers of fatty acids surrounding an internal space that could host RNA.

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"The one system still missing from these protocells is metabolism. This is particularly challenging because it means creating entire sequences of chemical reactions. In modern organisms, these are controlled by battalions of protein enzymes, which can’t have existed when life began. (my bold)

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"Of course, all this depends on the everything-first idea proving correct. Szostak’s protocells and the new biochemical insights have won over many researchers, but some pieces of the puzzle are still missing. Perhaps the most persuasive argument is that the simpler ideas don’t work. As is the case with many things in life, the beginning was probably more complicated than we had thought."

Comment: Finally, at the end some common sense. Goldilocks is God!!!