Birth Of Life: What Chemical Reactions Triggered First Organisms On Earth?

The formation of Earth and life on it is fascinating science. Following the course of life, we can see that complex multicellular organisms like us evolved from the simplest molecules and microorganisms. Now, a team of researchers have found the key chemical reactions that could’ve triggered life on Earth as we know it.

Chemists at The Scripps Research Institute (TSRI) have found out the key ingredients that formed the perfect environment for life on earth to blossom.

The researchers identified the components — a-ketoacids and b-ketoacids — as the primary materials needed for chemistry to work its wonders.

They say that these materials existed on Earth four billion years ago and their presence triggered the reactions that caused the first single-celled organisms to come into being.

The team of researchers from National Science Foundation/National Aeronautics and Space Administration (NASA) Center for Chemical Evolution were studying the series of chemical reactions known as the citric acid cycle .

"This was a black box for us," said Ramanarayanan Krishnamurthy, PhD, associate professor of chemistry at TSRI and senior author of the new study in a press release. "But if you focus on the chemistry, the questions of origins of life become less daunting."

The citric acid cycle performs one of the most crucial and basic function for life to sustain itself on this planet. This reaction is used to release energy stored in the cells to power life. The team of researchers pin-pointed this reaction as the crux to life formation on Earth. But in the first one billion years of Earth’s formation, as the spinning hot mass began to cool, a-ketoacids and b-ketoacids weren’t fully formed into their most stable state, which could have triggered the reaction.

The team instead used a top-down approach and calculated the time period the materials would have taken a stable form in our atmosphere. The new study started with the chemical reactions first. They figured out what will be required for the reaction to occur based on their knowledge of the reaction and then calculated when the condition would have been right for life to kick into being.

The team identified two more primitive processes or non-biological cycles—called the HKG cycle and the malonate cycle— that could have come together to start life. These two cycles create products of that are chemically the same as the products of the citric acid cycle.

These shared reactions include aldol additions, which bring new source molecules into the cycles, as well as beta and oxidative decarboxylations, which release the molecules as carbon dioxide (CO2) which is an integral gas to early atmosphere formation.

These reactions surprised the researchers. They found that reactions could produce amino acids in addition to CO2, which are also the end products of the citric acid cycle thereby giving the same product but a different pathway for the same reaction.

These amino acids would’ve helped the formation of enzymes. These enzymes, when introduced into the reaction, would have induced the biological factor, creating products with different biological properties, spawning the first life.

"The chemistry could have stayed the same over time, it was just the nature of the molecules that changed," says Krishnamurthy. "The molecules evolved to be more complicated over time based on what biology needed."

"Modern metabolism has a precursor, a template, that was non-biological," adds Greg Springsteen, PhD, first author of the new study and associate professor of chemistry at Furman University.

At the centre of these predicted processes is the molecule called glyoxylate, which studies show could have been available on early Earth and is part of the citric acid cycle today.

The team wants to analyze these precursors to the citric acid cycle. They want to study the processes further to understand how these chemical reactions could have become sustainable which would’ve populated the earth with organic material.

The study was published in journal Nature Communications on Jan. 8.