Understanding Origin of Life

We were having this discussion during the last two days here and I thought it would be interesting to compile related information for the inquisitive minds.

Carbon based life, as we know to have evolved on earth or around, is essentially due to the unique property of carbon to form three dimensional molecules of large sizes and complexities with other elements like hydrogen, oxygen, nitrogen and phosphorus. These large organic molecules, that have carbon atoms as the main binding element, can have varied chemical and physical properties based on the juxtaposition of some commonly found elements with respect to carbon atoms. These chains of molecules are complex compounds and are classed as amino acids, enzymes, sugars etc.

Also, it is known that the presence of water vastly increases the number of possible organic molecules, increasing the likelihood that the right combination of molecules for ‘life’ can form.

In the year 1999, some scientists in NASA were trying to test the theory that the seeds of life came to earth aboard meteorites and other space debris that bombarded the earth billions of years ago. Studies had shown that PAHs (polycyclic aromatic hydrocarbons) were the most abundant organic molecules in the universe. So a team of scientists, headed by a chemist, Max Bernstein, froze and then bombarded PAH molecules-attached to water ice, as they thought to have existed in space-with Ultraviolet light and thus simulating the natural conditions found in dust clouds in interstellar space. The results showed the creation of the basic organic chemicals, called the ‘building blocks’ for the development of life. These included quinones, aromatic ketones, alcohols and ethers.
Stanley Miller, a graduate chemistry student, in his research work on this subject, placed a mixture of gases-methane, ammonia, water vapor and hydrogen, simulating a model of primitive planetary atmosphere, into a pair of closed flasks connected by glass tubes. He rigged this experimental set-up so that he could pass electrical sparks through one of the flasks, simulating lightening. The results were amazing- complex organic molecules of amino acids, the building blocks of protein were seen to have formed. Their experiments produced all the 20 amino acids synthesized by life today as well as various sugars, and phosphates including the ones that form the backbone of RNA and DNA.

The development of even the most primitive form of life required many steps. First, the organic chemical ‘building blocks’ of life, such as amino acids must have been available from some source. Second, these building blocks somehow assembled into longer and more complex organic molecules and at some point RNA must have come into existence. RNA is capable not only of passing on molecular information but also stimulating the chemical reactions for protein formation.

So, life must have begun in the primitive ‘RNA World’ as selfish molecules that existed only to reproduce themselves. The first selfish molecule would have been a simple RNA with a very short sequence of nucleotide bases. Unlike modern day RNA, these hypothesized early RNA molecules could catalyze chemical reactions, snatching chemical building blocks from surrounding waters and using these building blocks to make copies of them. If random changes-mutations-in the molecular structure of a single primitive RNA allowed it to produce an attached enzymatic protein that happened to speed the RNA’s reproduction, the pair of molecules would proliferate at the expense of all others.
This scenario is not unreasonable. Present day viruses frequently mutate and develop into more hardy strains, which can quickly multiply.

And finally, if RNA and its helper enzymes begin to synthesize molecules that form a sealing membrane, that protects it from variability of outside environment, the RNA might be able to proliferate even further. And then something that could be called life would exist.

I would reason out the existence of life to Carbon’s bonding properties, right activation energy levels for chemical reactions, right surrounding chemistry and finally a series of good ‘mistakes’ or mutations in the RNA molecules during duplication of structures, wherever they may have occurred-either on earth or around it.