Fatty acids prebiotic synthesis

The term chemical evolution" was introduced by the Nobel Prize winner Melvin Calvin and refers to the process of the synthesis of biochemically important molecules from small molecules and certain chemical elements under the (hypothetical) conditions present on prebiotic Earth. It is assumed that the smaller building block molecules such as amino acids, fatty acids or nucleobases were formed initially, and that these underwent polycondensation to give macromolecules in later stages of development. 

More convincing evidence has been obtained for the synthesis of simpler compounds, such as straight-chain fatty acids. This observation is important because, as we have already seen in the chapter on self-organization and self-reproduction, these compounds form stable vesicles. Prebiotic synthesis of these compounds was reported for example by Nooner et al. (1976). More recently monocarboxylic acids have been observed from a spark discharge synthesis (Yuen et al, 1981) and from a Fischer-Tropf type of reaction (McCollom et al, 1999 Rushdi and Simoneit,... 

The competition among protocells for membrane components could drive rapid evolution of sophisticated membranes. While fatty acids were likely to be available through prebiotic synthesis, the synthesis of phospholipids may have required enzymatic activity, such as a ribozyme that could catalyse condensation of fatty acids with phosphate head groups. If such an activity arose, protocells containing phospholipids would be able to hold on to their fatty acids more tightly, in the sense that the rate constant for dissociation of the fatty acids from the bulk phase is reduced by the presence of the bipartite lipid. In addition, the dissociation rate for bipartite lipids themselves is also much lower than that of fatty acids. Both effects... 

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