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Protocell Emergence and Evolution

Authored by: Punam Dalai , Nita Sahai

Handbook of Astrobiology

Print publication date:  December  2018
Online publication date:  December  2018

Print ISBN: 9781138065123
eBook ISBN: 9781315159966
Adobe ISBN:

10.1201/b22230-34

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Abstract

The cell is the generally accepted simplest unit of life and is defined by its membrane. In addition to membrane lipids, nucleic acids and proteins are the essential biomolecules common to all forms of life. Understanding how the monomers of these molecules emerged prebiotically under geologically plausible conditions, polymerized, and self-assembled to form the earliest self-sustaining and self-replicating unit or protocell is the quest of those who seek to model the bottom-up self-assembly of the first life. Protocells are believed to have had membranes composed primarily of single-chain amphiphiles (SCAs) among other suggestions such as mineral membranes. Compartmentalization offered many potential benefits to the emergence and evolution of protocells such as concentrating solutes, including biomolecule monomers and oligomers within the membrane, competition between different populations of protocells, transmembrane mass and energy transport necessary for the development of bioenergetics (protometabolism), and rudimentary self-replication. Studies on model protocell systems consisting of SCA vesicles interacting with ribonucleotides and peptides under a range of aqueous geochemical environments as well as efforts to model protocell metabolisms are summarized here. It is proposed that cooperative interactions and synergistic catalytic effects between oligoribonucleotides, oligopeptides, and membrane lipids ultimately lead to more complex molecules, with folding and function in protocells with increasingly life-like functions.

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