Living things are made of complex organic molecules – so where did those complex molecules come from?
Origin-of-life chemists have a suite of theories for how the first living molecules formed. Amino acids and nucleobases, which are key parts of proteins and DNA respectively, have fairly well-established beginnings. But sugars – another key part of DNA and RNA – are less well understood.
Read more: Why did ATP become so crucial for all life on Earth?
It’s commonly thought that they may have started with a compound called formaldehyde (CH2O).
A pair of US researchers have suggested a different theory: published in Chem, they think that a compound called glyoxylate (C2HO3–) is the more likely culprit.
Glyoxylate has featured in other origin-of-life theories too, as a basis for a number of other molecules crucial for life.
“We show that our new hypothesis has key advantages over the more traditional view that early sugars arose from the chemical formaldehyde,” says Professor Ramanarayanan Krishnamurthy, from the Department of Chemistry at Scripps Research Institute, US.
“The formaldehyde reactions proposed by this theory are quite messy – they have uncontrolled side reactions and other drawbacks due to formaldehyde’s high reactivity under the envisioned early-Earth conditions,” says Professor Charles Liotta, an emeritus professor at the Georgia Institute of Technology’s School of Chemistry and Biochemistry.
Instead, the researchers’ “glyoxylose reaction” starts with glyoxylate first reacting with itself, then with its own by-products in a chain until they become complex enough to form sugars.
While they’ve worked out a series of chemical reactions that make sense in theory, the researchers haven’t shown that this works in a laboratory yet: that’s next on their list.
“Such a demonstration would expand the role of glyoxylate as a versatile molecule in prebiotic chemistry and further stimulate the search for its own origin on the prebiotic Earth,” says Krishnamurthy.
This reaction also consumes CO2, meaning that – if it does work in practice – it could be a very effective carbon capture method.
Originally published by Cosmos as Sugar, spice and the origin of life: new theory for the first sugars
Ellen Phiddian
Ellen Phiddian is a science journalist at Cosmos. She has a BSc (Honours) in chemistry and science communication, and an MSc in science communication, both from the Australian National University.
Read science facts, not fiction...
There’s never been a more important time to explain the facts, cherish evidence-based knowledge and to showcase the latest scientific, technological and engineering breakthroughs. Cosmos is published by The Royal Institution of Australia, a charity dedicated to connecting people with the world of science. Financial contributions, however big or small, help us provide access to trusted science information at a time when the world needs it most. Please support us by making a donation or purchasing a subscription today.