The Origins of Cellular Life (original) (raw)

Models of primitive cellular life: polymerases and templates in liposomes

Philosophical Transactions of the Royal Society B: Biological Sciences, 2007

Nutrient transport, polymerization and expression of genetic information in cellular compartments are hallmarks of all life today, and must have appeared at some point during the origin and early evolution of life. Because the first cellular life lacked membrane transport systems based on highly evolved proteins, they presumably depended on simpler processes of nutrient uptake. Using a system consisting of an RNA polymerase and DNA template entrapped in submicrometre-sized lipid vesicles (liposomes), we found that the liposome membrane could be made sufficiently permeable to allow access of ionized substrate molecules as large as nucleoside triphosphates (NTPs) to the enzyme. The encapsulated polymerase transcribed the template-specific base sequences of the DNA to the RNA that was synthesized. These experiments demonstrate that units of genetic information can be associated with a functional catalyst in a single compartment, and that transcription of gene-sized DNA fragments can be achieved by relying solely on passive diffusion to supply NTPs substrates.

Recent Advances on the Origin of Life–Making Biological Polymers

The creationism–evolution debate almost always comes around to discussions about the or-igin of life. The enormousness of the problem of how organic chemicals (those compounds that contain the element carbon) reacted to synthesize biological molecules like proteins, nucleic acids, membrane lipids, and others, and how these self-replicated and assembled to form the first protocells, represents an attractive target for critics. In addition, the respect-able degree of uncertainty that surrounds present answers to origin-of-life questions, and the large diversity of the proposed solutions, represent ample fodder for those who would question the validity of the entire origin-of-life research program. Consequently, creation-ists have said a great deal about origin-of-life research, and none of it is positive. According to the doyen of recent (or "young-earth") creationist debaters, Duane Gish, the facts "establish beyond doubt that an evolutionary origin of life on this pla...

Life Began When Evolution Began: A Lipidic Vesicle-Based Scenario

Origins of Life and Evolution of Biospheres, 2009

The research on the origin of life, as such, seems to have reached an impasse as a clear and universal scientific definition of life is probably impossible. On the contrary, the research on the origin of evolution may provide a clue. But it is necessary to identify the minimum requirements that allowed evolution to emerge on early Earth. The classical approach, the ‘RNA world hypothesis’ is one way, but an alternative based on nonlinear dynamics dealing with far-from-equilibrium self-organization and dissipative structures can also be proposed. The conditions on early Earth, near deep-sea hydrothermal sites, were favorable to the emergence of dissipative structures such as vesicles with bilayer membranes composed of a mixture of amphiphilic and hydrophobic molecules. Experimentally these vesicles are able to self-reproduce but not to evolve. A plausible scenario for the emergence of a positive feedback process giving them the capability of evolving on early Earth is suggested. The possibilities offered by such a process are described in regard to specific characteristics of extant biological organisms and leads for future research in the field are suggested.

The Role of Lipid Membranes in Life's Origin

Life (Basel, Switzerland), 2017

At some point in early evolution, life became cellular. Assuming that this step was required for the origin of life, there would necessarily be a pre-existing source of amphihilic compounds capable of assembling into membranous compartments. It is possible to make informed guesses about the properties of such compounds and the conditions most conducive to their self-assembly into boundary structures. The membranes were likely to incorporate mixtures of hydrocarbon derivatives between 10 and 20 carbons in length with carboxylate or hydroxyl head groups. Such compounds can be synthesized by chemical reactions and small amounts were almost certainly present in the prebiotic environment. Membrane assembly occurs most readily in low ionic strength solutions with minimal content of salt and divalent cations, which suggests that cellular life began in fresh water pools associated with volcanic islands rather than submarine hydrothermal vents.