Water The Solvent for Biochemical Reactions

This idea is easily extended to our own chemistry— because 60% of our bodies is water, we should appreciate the polarity of water on a hot day. As a biological solvent in the human body, water is involved in the transport of ions, nutrients, and waste into and out of cells. Water is also the solvent for biochemical reactions in cells and the digestive tract. Water is a reactant or product in some biochemical processes. 

Fig. 8 depicts mass indices S-1 and environmental factors E and gives an indication of the mass efficiency for the four routes A-D. The amounts of chemicals needed for the production of 1 kg HPB ester varied between approximately 40 kg and 105 kg. In all cases, the major components were water and the solvents needed for the reactions and/or extractions, a picture that is typical for fine chemical synthesis. Route D clearly had the lowest consumption of materials. The main drawback for the two biochemical routes A and B were the need for rather large amounts of water and solvents (for extraction), even though it has to be pointed out that these processes were not optimized. Comparable variations were observed for the substrate consumption, i.e., how much starting material was needed to produce 1 kg of HPB ester (see Fig. 8b). In this case, however, both the highest (C) and the lowest (D) consumptions were observed for the chemical routes. The...

During these studies, it became apparent that proton transfer is an extremely sharp instrument for gauging the water in the immediate environment surrounding the site of dissociation. It turned out that the general biological solvent, the water, acquires different properties at the site where biochemical reaction takes place—the surface of the enzyme. These local properties of the water can be measured through the technique of the laser-induced proton pulse, free of perturbation caused by the huge mass of the bulk water. 

Initially, most theoretical methods calculated the properties of molecules in the gas phase as isolated species, but chemical reactions are most often carried out in solution. Biochemical reactions normally take place in water. Consequently, there is increasing interest in methods for including solvents in the calculations. In the simplest approach, solvents are treated as a continuum, whose average properties are included in the calculation. Explicit inclusion of solvent molecules in the calculation greatly expands the size of the problem, but newer approaches do this for at least those solvent molecules next to the dissolved species of interest. The detailed structures and properties of these solvent molecules affect their direct interaction with the dissolved species. Reactions at catalytic surfaces present an additional challenge, as the theoretical techniques must be able to handle the reactants and the atoms in the surface, as well as possible solvent species. The first concrete examples of computationally based rational catalyst design have begun to appear in publications and to have impact in industry. 

But there is more to water than its role as solvent, since, like oxygen, it is also a reagent (as well as a product, but this aspect is irrelevant here) in innumerable biochemical reactions. This is the biochemical role of water, a double one, in fact. First and foremost, water is a reagent in innumerable lifesupporting reactions. Secondly, and like for oxygen, evolution has recruited water as a major player in the detoxification and elimination of xenobiotics. This biological function of water, we believe, is presented here for the first time in its full depth and breadth. 

You are made of water, born into a world of water, and then forevermore dependent on water. You can survive for more than a month without food, but without fresh water you would perish in a matter of days. Little wonder when you consider that water makes up about 60 percent of your body mass. It s the ideal solvent for transporting nutrients through your body and for supporting the countless biochemical reactions that keep you alive. All living organisms we know of depend on water. It is the medium of life on our planet and arguably our most vital natural resource. 

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