Formation of Polymers
Formation of Polymers
The next stage in chemical evolution involved the condensation of amino acids, nitrogenous bases, and sugars to yield larger molecules, such as proteins and nucleic acids. Such condensations do not occur easily in dilute solutions, because the presence of excess water tends to drive reactions toward decomposition (hydrolysis). Although the primitive ocean might have been called a “primordial soup,” it was probably a rather dilute one containing organic material that was approximately one-tenth to one-third as concentrated as chicken bouillon.
Need for Concentration
Prebiotic synthesis must have occurred in restricted regions where concentrations of the reactants were high. Violent weather on the primitive earth would have created enormous dust storms; impacts of meteorites would have lofted great amounts of dust into the atmosphere. The dust particles could have become foci of water droplets. Salt concentration in the particles could have been high and provided a concentrated medium for chemical reactions. Alternatively, perhaps the surface of the earth was too warm to have oceans but not too hot for a damp surface. This condition would have resulted from constant rain and rapid evaporation. Thus, the earth’s surface could have become coated with organic molecules, an “incredible scum.” Prebiotic molecules might have been concentrated by adsorption on the surface of clay and other minerals. Clay has the capacity to concentrate and condense large amounts of organic molecules. The surface of iron pyrite (FeS2) also has been suggested as a site for the evolution of biochemical pathways. The positively charged surface of pyrite would attract a variety of negative ions, which would become bound to its surface. Furthermore, pyrite is abundant around hydrothermal vents, compatible with the hydrothermal-vent hypothesis.
The next stage in chemical evolution involved the condensation of amino acids, nitrogenous bases, and sugars to yield larger molecules, such as proteins and nucleic acids. Such condensations do not occur easily in dilute solutions, because the presence of excess water tends to drive reactions toward decomposition (hydrolysis). Although the primitive ocean might have been called a “primordial soup,” it was probably a rather dilute one containing organic material that was approximately one-tenth to one-third as concentrated as chicken bouillon.
Need for Concentration
Prebiotic synthesis must have occurred in restricted regions where concentrations of the reactants were high. Violent weather on the primitive earth would have created enormous dust storms; impacts of meteorites would have lofted great amounts of dust into the atmosphere. The dust particles could have become foci of water droplets. Salt concentration in the particles could have been high and provided a concentrated medium for chemical reactions. Alternatively, perhaps the surface of the earth was too warm to have oceans but not too hot for a damp surface. This condition would have resulted from constant rain and rapid evaporation. Thus, the earth’s surface could have become coated with organic molecules, an “incredible scum.” Prebiotic molecules might have been concentrated by adsorption on the surface of clay and other minerals. Clay has the capacity to concentrate and condense large amounts of organic molecules. The surface of iron pyrite (FeS2) also has been suggested as a site for the evolution of biochemical pathways. The positively charged surface of pyrite would attract a variety of negative ions, which would become bound to its surface. Furthermore, pyrite is abundant around hydrothermal vents, compatible with the hydrothermal-vent hypothesis.
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