General ---------Biology ------------------Online-------------------------- Ch.  3:  Water and the fitness of the environment

Water is important in cell biology for two primary reasons:

1.  Water is the solvent for all the various chemicals that react form life.

When you order a sample of He La Cells (Henrietta Lacks' cervical cells) they arrive a
"lifeless" freeze dried powder.  Add water, and the chemical reactions that animate life begin;  cells crawl around, find partners and begin to reassemble as ovarian tissue.

Many of the amino acids, sugars and enzymes that make up our cells must be dissolved in water to function.  Thus, Water is the solvent of Life.

2.  Water moderates the temperature on earth, allowing life to exist.

Water changes temperature very slowly compared to most other things.  If you put water in a metal pot on the stove to boil, in only a few seconds the metal handle warms and soon is too hot to touch.  The water in the pan is still cold.  Water is pervasive on earth:  in our atmosphere as water vapor (a gas); it is the solvent of our oceans (a liquid) that make up 3/4 of the planet; it is in our massive polar ice caps as ice (a solid).  It is also in our soil, and makes up 70% to 95% of the weight of plant and animal cells.  Water's pervasive distribution, combined with its resistance to sudden temperature change, causes earth's temperature to be quite moderate compared to other planets.

The surface temperature on earth swings about 70 degrees during a 24 hr. period, whereas on the surface of the dry moon the temperature swings 140-200 degrees during the same period. 

Summary:  Students should write summary statements below as bullet points.
 
 

Test your knowledge:  Practice Quiz # 5.  Be able to recognize all three models of water.