How life arose on Earth is among the most important mysteries in science. Although it’s still an open question in biology, scientists have some promising theories about how a chemical soup eventually created complex cellular life some 3.7 billion years ago. But a theory is more than a good guess—it needs to explain the available evidence, and it also needs to be testable.
Scientists believe that amino acids were present in abundance in the early years of the Earth, and that these pieces contributed to the formation of the first cell.
There is ample data indicating that single-celled organisms emerged slowly from the random aggregation of chemicals floating in the water. For example, we can see the signatures of ancient life in the form of microbial matsThese are sheets of dead, fossilized microbes that form in sediments or on rock surfaces. We can estimate their age through radiometric dating and chemical analysis, which gives us a sense of when life began.
We can even test this theory, using experiments that simulate our best estimates of what the ancient Earth was like. In 1952, the Miller-Urey experiment, for example, simulated the conditions of Earth’s early atmosphere by running electrical sparks through a mixture of gases (mainly methane, ammonia, and hydrogen). The experiment produced several organic compounds, including amino acids, which are the building blocks of proteins. In fact, scientists believe that amino acids were present in abundance in the early years of the Earth, and that these pieces contributed to the formation of the first cell.
Amino acids are like letters of the alphabet, and proteins are like words. With enough proteins, you can form “camels”—in this case, biological pathways that are a bit like microspheres Rube Goldberg machines that allow life to do everything.
Most biologists do not consider proteins to be alive. They are large, complex molecules made up of long chains of amino acids, which are essential to the structure and function of all living things. So where do you draw the line between protein release and organism? It is about those pathways, which are governed by the rules of biology, which we call DNA.
In other words, understanding how life got started means discovering how DNA was formed in the first place. Understanding what Earth looked like before life emerged – and what kinds of amino acids and proteins were orbiting around it – means we’re one step closer to understanding how life arose.
Although hundreds of different amino acids may have been present in the early Earth, all living things depend only on about 20 of these compounds.
Now, a new study in Journal of the American Chemical Society It suggests that evolution began long before life appeared and that proteins are about primordial soups chosen for preferred traits. In other words, there was a kind of effect of Darwinian selection (even before the emergence of life) between the non-living proteins and amino acids in the primordial soup.
This idea explains why, although there were hundreds of different amino acids on the early Earth, all living things depended only on about 20 of these compounds. So why were these specific amino acids chosen?
“You see the same amino acids in every living organism, from humans to bacteria to archaea, and that’s because all things on earth are connected through this tree of life that has an ancestry, an organism that was the ancestor of all living things,” Stephen Frieda chemist at Johns Hopkins University who co-led the research with scientists at Charles University in the Czech Republic, said V statement. “We describe the events that shaped why this ancestor obtained the amino acids it did.”
While there are 20 important amino acids, mounting evidence indicates that ancient life first arose. using only 10. To test this, the experimenters created several different libraries of different combinations of amino acids and then screened them for two things: their solubility and propensity for secondary structure. It sounds complicated (and it is) but these terms simply relate to the proper forms of proteins.
The shapes of a protein and how it folds is critical to its function. This determines how it interacts with other molecules and their environment. Think of them like paper origami paper It can be folded into many different styles.
So by testing which libraries had the best solubility and structure, researchers could conclude that proteins were evolving and driving natural selection before organisms were even formed. Over time, proteins that were the best form of biochemical processes were incorporated into the basic cycles of life.
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“The protein folding was basically allowing us to carry out evolution before there was life on our planet,” Fried said. “You could have evolution before you had biology, you could have natural selection of chemicals beneficial to life even before there was DNA.”
“For you to have evolution in the Darwinian sense, you have to have this complex way of turning genetic molecules like DNA and RNA into proteins. But DNA transcription also requires proteins, so we have the chicken-and-egg problem,” Fried added. “Our research shows that nature could have selected building blocks with beneficial properties before Darwinian evolution.”
Of course, the more we study how life formed on our own planet, the better we can appreciate how life formed on other planets. amino acids abundant in asteroidsindicating that conditions for the spawning of alien life forms exist in other corners of the universe.
“The universe seems to love amino acids,” said Fred. “Maybe if we found life on a different planet, it wouldn’t be so different.”
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