![]() |
|
#11
|
||||
|
Quote:
First, life needed an energy source to bring about the condensation reaction that yielded the peptide bonds of proteins and the phosphodiester bonds of RNA. In a generalization and thermal variation of the binding change mechanism of today's ATP synthase, the "first protein" would have bound substrates (peptides, phosphate, nucleosides, RNA 'monomers') and condensed them to a reaction product that remained bound until after a temperature change it was released by thermal unfolding. The energy source under the thermosynthesis hypothesis was thermal cycling, the result of suspension of protocells in a convection current, as is plausible in a volcanic hot spring; the convection accounts for the self-organization and dissipative structure required in any origin of life model. The still ubiquitous role of thermal cycling in germination and cell division is considered a relic of primordial thermosynthesis. By phosphorylating cell membrane lipids, this "first protein" gave a selective advantage to the lipid protocell that contained the protein. This protein also synthesized a library of many proteins, of which only a minute fraction had thermosynthesis capabilities. As proposed by Dyson,[172] it propagated functionally: it made daughters with similar capabilities, but it did not copy itself. Functioning daughters consisted of different amino acid sequences. Whereas the iron-sulfur world identifies a circular pathway as the most simple—and therefore assumes the existence of enzymes—the thermosynthesis hypothesis does not even invoke a pathway, and does not assume the existence of regular enzymes: ATP synthase's binding change mechanism resembles a physical adsorption process that yields free energy,[173] rather than a regular enzyme's mechanism, which decreases the free energy. The RNA world also implies the existence of several enzymes. It has been claimed that the emergence of cyclic systems of protein catalysts is implausible.[174]" There is the answer for you. Hope you understand it. | |||
|
|
||||
|
|