Tầm quan trọng của nước trong sinh học nổi tiếng: sự sống trên trái đất không thể tồn tại mà không có nước. Có một số lượng lớn của nước trong các sinh vật sống (khoảng 60% tính theo trọng lượng trong cơ thể con người), cả hai bên trong và bên ngoài các tế bào sinh học. | This page intentionally left blank 6 Role of interfacial water in biological function Importance of water in biology is well known life on the earth cannot exist without water. There is a large amount of water in living organisms about 60 by weight in human body both inside and outside the biological cells. Water is involved in various biochemical reactions and acts as a solvent for biomolecules. Despite the relatively high water content in living organisms pure liquid water is practically absent in biosystems. Both intracellular and extracellular liquids consist mainly of water but the concentration of organic compounds including large biomolecules is very high about 20 to 30 . The central role of water in biological function is recognized 442 443 but the numerous questions concerning the physical mechanisms behind the importance of water for life remain unanswered. There are several important physical phenomena which should be taken into account when considering water properties in biosystems and the role of water in biological function. First phenomenon is related to the bulk phase transitions in aqueous mixtures. In biosystems water is a component of a multicomponent fluid mixture with various biomacromolecules small organic molecules ions etc. This complex mixture unavoidably possesses a rich phase diagram with numerous phase transitions and respective critical points which may occur close to the thermodynamic conditions typical of living organisms on the earth. The general features of these phase transitions are similar to the ones of the liquid-liquid transitions of binary mixtures of small organic molecules with water. However there are several factors that make the phase transitions in biological liquids much more complex. Multiplicity of the transitions in a multicomponent mixture assumes multiplicity not only of the stable but also of the metastable states which may exist during a long period of time. Phases enriched with macromolecules are usually not .
