Water, Critical Fluid of Cells and Chemistry
Water is a Compound and Solvent Crucial to Life and Its Functions
Sep 1, 2009
It is hard to imagine that life without water would be possible. Living cells can be freeze-dried and will survive for years or decades in the absence of water. Later, when water is added, these cells once again become active. The re-constituted cells metabolize, grow and divide – they are alive!
Water, Hydrogen Bonding, Bipolarity and Attractions
Water is a unique compound, composed of two hydrogen atoms, covalently bonded to one oxygen atom. The water molecules show bipolarity, i.e. an electronic distribution that gives one part of the molecule a negative charge around the oxygen atom, and an overall positive charge around the hydrogen atoms. Therefore, water molecules behave as mini-magnetic molecules with opposite charges attracting and like charges repelling one another. Bipolarity causes water to have some degree of structure that extends beyond the individual molecules and cause a community water effect. The overall property is called hydrogen bonding, i.e. the attraction of the hydrogen nucleus (a proton) for electronegative regions of other atoms like oxygen.
Pure Water has Important, Distinctive and Unique Properties
The important and unique properties of water are:
- excellent solvent, i.e. many compounds dissolve in water and form solutions; larger molecules suspend, but do not dissolve. Examples: many salts, sugars, amino acids dissolve, and many larger molecules form colloids that float, suspended, within water.
- most dense at 4 degrees C – these water molecules sink.
- least dense at O degrees Centigrade; water turns from a liquid to a solid and forms distinctive ice crystals that float.
- high surface tension, makes floating on water surfaces possible.
- capillarity; water molecules tend to orient and stick to one another and move through narrow channels as in plant vessels.
- high specific heat and heat of vaporization. It requires 1 calorie to raise 1 gram of water 1 degree Centigrade, and 540 calories to cause 1 gram of water to change from a liquid to a vapor. This means that water has an ability to retain heat, and when water evaporates it carries heat with it. Therefore, sweating or panting has a cooling effect that protects animals from excess body heat.
- small molecular size and kinetic energy contribute to Brownian motion of larger molecules and particles.
Why Pure Water is Needed for Life and Many Chemical and Biochemical Reactions
It is difficult to imagine how life without water could ever be. Compounds dissolved in water, and other molecules suspended in water, move about freely and distribute. This situation permits multiple interactions among the many different molecules and types of compounds. In a dry, or frozen state, these types of motions and free associations are limited and do not happen. Therefore, intra- and intercellular molecular movements are promoted by water.
Pure Water is Vital and Essential to Life and Health
The need for pure and healthy waters should be clear to all. Water should be free of compounds, elements and toxins that could do harm to cells and organisms. Protection of all of earth sources, especially water, is important. Streams, rivers, lakes, underground waters, earth's oceans and seas, all abound with life and good nutrients. Whenever pollution occurs, the pollutants change the quality of the water and make it harmful to life that needs that water to live. Microbes and both natural and artificial filtration contribute to purify water for human consumption.
All are called to be good stewards of the planet. When people pollute water and air they cause immediate and potential, long-term damage. This introduction reminds all to contribute and help protect water resources critical to daily life.
Resource
Alters, S and B. Alters. 2006, Biology. John Wiley & Sons Inc., Hoboken, N.J. 755 pp
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