Did the building blocks of life form inside of water droplets?
In our bodies, genetic codes describe the ways in which amino acids get assembled into chains known as peptides, which then form the building units of proteins. The formation of peptide bonds is one of the most important biochemical reactions and, in our cells, it is catalyzed (sped up) by enzymes in order to produce essential proteins quickly. But how did the very first proteins get assembled, before there were any living cells or enzymes to assist the process?
Earth did not always harbor life. In fact, for around 500 million years there was no life at all. But sometime around 4 billion years ago, something in the environment changed, and systems with biological properties began to emerge. Although amino acids of many different types were present before this, they were now able to assemble themselves into peptide chains, and later into proteins. Scientists have pondered how the chemistry of the early Earth may have facilitated the origin of these proteins, and have come up with many theories. However, there has been little experimental laboratory support for these ideas.
If, as scientists have theorized, life on Earth began in the oceans, then amino acids – which were considered to be abundant in these times – would have joined together by means of peptide bonds while surrounded by a watery medium. But the formation of a peptide bond between two amino acids requires the removal of a molecule of water, a process known as dehydration synthesis. Chemists have always thought this was rather unlikely to occur in a wet, aqueous or oceanic environment, especially without the presence of any catalyst to speed up the reaction.