Scientists have received a new explanation for how life could arise on Earth. Presumably, the metabolism appeared before RNA.
Researchers have presented evidence of primitive biochemistry without phosphates, an essential nucleic acid component of the building blocks of our genetic chemistry, fueling the argument that before there was life, there was metabolism. Scientists at the Massachusetts Institute of Technology and Boston University have identified a number of alternative metabolic pathways that have no phosphate requirement - and the results could fill a gap in our understanding of how complex organic chemistry evolved into life on Earth.
Life as we define it today is largely based on imperfect replication of chemistry - something that requires a template that can be copied and the means to capture enough energy and physically rearrange simple, chemical-based carbons into more complex forms.
In the so-called RNA world hypotheses, strings of free floating ribonucleic acid (RNA) facilitated processes that we might describe as precursors of life. One problem with this concept is that RNA cannot do its job without a source of energy, as it would require a sequence of chemical reactions. This is what scientists call an early form of metabolism. Not only that, the RNA molecule includes phosphate, a molecule that has been trapped in the environment and therefore difficult to incorporate into organic compounds.
Eventually, this primitive metabolism began to combine with RNA, and over time found refuge inside individual fat bubbles - objects that we could consider as the first cells. Metabolism in modern organisms, however, is largely based around compounds like adenosine triphosphate (ATP) and nicotinamide adenine dinucleotide phosphate (NADP), which once again includes this nasty old phosphate molecule.
Alternative metabolic pathways that are currently being identified by researchers are based on molecules built using sulfur that were abundant in Earth's oceans several billion years ago.
Roman Klaviaturovich