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BIOLOGY AND PATHOLOGY OF WATER* ALBERT SZENT-GYÖRGYIj Mater and Matrix Life was born in water and is carrying on in water. Water is life's mater and matrix, mother and medium. There is no life without water. Life could leave the ocean when it learned to grow a skin, a bag in which to take the water with it. We are still living in water, having the water now inside. The ionic composition of our blood still reflects the ionic composition ofthe primordial ocean. It is a queer fact that we should have kept this ionic concentration more constant than the ocean itself, which has changed since we left it. Water is part and parcel of the living machinery . I always felt that this machinery consists oftwo parts: the "solid" and water structures it induces. Life could actually have started with inducing these structures which it used as its instruments. Though my own body consists of 80 percent water and only 20 percent solid, and ifyou would shut me into a desiccator I would dry down to 15 kilograms, I always felt that my 75 kilograms are all me and I am not merely 15 kilograms plus water. It is true that you could replace my water lost in the desiccator by water from the tap, but the same is true, in a way, forevery molecule ofthe solid, too. You couldexchange any ofthemwith an identical synthetic one without altering my personality. Biology has forgotten water, or never discovered it. According to Sir Oliver Lodge the last thing a deep-sea fish would discover is water. Physical Properties The water molecule has a peculiar shape (fig. 1). On the one side its two hydrogens are sticking out with their positive formal charge, while * Lecture given at the Physiology Course of the Marine Biological Laboratory, Woods Hole, Massachusetts. t Institute for Muscle Research, Marine Biological Laboratory, Woods Hole, Massachusetts. Work supported by grant GB 8645 ofthe National Science Foundation. 239 on the opposite side the lone pair of electrons is protruding, lending a negative charge to this end of the molecule. In rapid rotation the whole structure would look to the observer like a small sphere of2.76 angstroms diameter. Figure ? intends to give only the shape of the water molecule. Like other molecules, this water molecule, too, is but an electron cloud without such sharp outlines as suggested by the figure. The most striking physical quality ofwater is its strong dipole character, which makes charges attract it. Ions will thus clad themselves with a sheet ofwater molecules which they hold strongly. Outside this sheet we Fig. i.—Shape ofthe water molecule. Redrawn after R. H. Horne, Marine Chemistry (New York: Wiley Interscience, 1969). can expect a second sheet ofmore loosely held water. Frank and Evans [1] called this water structure formed around ions, in a rather picturesque way, "icebergs," by which they did not mean to say that the bound water had the crystal structure ofice. They meant to express only that the water was strongly bound. This water envelope modifies the interactions ofthe ion in various ways. If we consider permeability, the actual dimension to be reckoned with will not be the diameter of the ion itself but, rather, that ofthe "iceberg." Iftwo ions collide, it will be water sheaths which collide, acting as bumpers. This bumper action will be especially strong if two equally charged ions tend to collide. If, say, both ions have a positive charge, then water dipoles surrounding them will turn their negative end outward, repelling one another. If the two ions have an opposite charge, they will contribute to mutual attraction, turning their oppositely charged sides outward. This attraction may partly be responsible for the "binding" ofions. According to Ling [2] the K+ ions ofcells are not free but are bound to the protein which has a prevailing negative charge. The 240 Albert Szent-GySrgyi · Biology of Water Perspectives in Biology and Medicine · Winter 1971 permeability of an ion through a pore will also have to depend on the charge of the wall of the pore and the charge of the outer sheet of the "iceberg." Identical charges will disfavor permeability. Chemical Properties...