The Organic Structures of Biology

Esters of carboxylic acids are prominent among the chemical structures of biological systems. The biosyntheses of only a few of the naturally occurring esters have been studied enzymatically. Among the known reactions are the syntheses of acetylchohne and of phosphatidic acids. Acetylcholine is formed by choline acetylase, which has been purified from nervous tissue. Nachmansohn and associates have prepared choline acetylase from rat brain, the electric organ of the electric eel, squid ganglia, and other tissues. It has been detected in muscle also, but not in liver or kidney. The reaction is very similar to the acetylation of amines. 

The self-organization of lipids to form the plasma membrane [1] was a crucial step in the evolution of the earliest forms of life. Whereas Ae lipid bilayer determines the basic structure of biological membranes, most of their functions are provided by proteins embedded in the lipid bilayer. However, the structure of the cell membrane is so complex that it is diffcult to study specific individual processes in biological systems. This is why it is an advantage to choose model membranes for investigating biomembrane processes because they can be limited to a few variable factors. Figure 2 outlines various membrane processes which can be simulated with monolayers as model membrane systems. 

In biological systems molecular assemblies connected by non-covalent interactions are as common as biopolymers. Examples arc protein and DNA helices, enzyme-substrate and multienzyme complexes, bilayer lipid membranes (BLMs), and aggregates of biopolymers forming various aqueous gels, e.g, the eye lens. About 50% of the organic substances in humans are accounted for by the membrane structures of cells, which constitute the medium for the vast majority of biochemical reactions. Evidently organic synthesis should also develop tools to mimic the Structure and propertiesof biopolymer, biomembrane, and gel structures in aqueous media. 

Finally, it can be envisaged that the future development of novel bio-nanohybrids will lead to new improved properties and multifunctionality derived from the synergistic combination of nanosized inorganic solids, with different structural and textural features, with molecular or even highly organized species of biological origin that are extraordinarily abundant in Nature. 

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