2013, Number S1
Perinatol Reprod Hum 2013; 27 (S1)
Fuentes AM, Amábile-Cuevas CF
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ABSTRACTWater plays a crucial role in biology. The simple H2O molecule has unusual physical chemical properties, due to its structure in liquid state which is still a matter of debate. It establishes hydrogen bonds, between them and with other molecules with electrical charge, which defines the hydrosolubility of such molecules. Prebiotic evolution privileged those chemical reactions that occur in water, and their confinement in lipid vesicles, which resulted in the first cells. Most bio-molecules are water-soluble or amphipathic; water organizes around them in solvation spheres, which have a key role in their biological function. The way water organizes around ions probably explains their intra-cellular or extra-cellular location. In addition of being the solvent for most biochemical reactions, water is also needed or formed by many of them. It is impossible to generalize about the amount of water that humans need on physiological basis. Thirst is, however, a reliable indicator of the need to drink water. However, some diseases and age-groups may not entirely rely on thirst to drink enough water; for them it would be necessary to formulate algorithms, better than allowance recommendations. Water is also needed for the disposal of soluble waste. Renal function is tightly regulated by the renin-angiotensin-aldosterone system that coordinates renal and cardiovascular function, as well as thirst.