Tutoring biology 12, the six (or so) functions of water in the human body comprise an early theme.

Everyone knows water is important in the human body, but what are the precise reasons?

1.  Water is liquid at body temperature.  This point is obvious, yet important.

2.  Water is a very effective solvent.  It doesn’t dissolve everything, of course:  if it did, you wouldn’t have a body.  However, water is very good at dissolving salts as well as simple organic molecules that can form H-bonds (sugars, for example).

3.  Water molecules are strongly attracted to each other, so stick together.  Therefore, water beads on a table surface when spilled, and water also can be drawn upwards in a straw.

Water’s tendency to stick together (also called cohesiveness) causes it to move along in a unified manner.  Anything in the water must move with it, since the water molecules pull each other along.  Hence, water is the transport medium  in the human blood system.

4.  Water can release a great deal of heat without cooling down much.  It can also absorb a great deal of heat while only slightly increasing its temperature.  Therefore, water stabilizes the body’s temperature.  As we’ll discuss in later posts, the body works best when its temperature stays at 37°C.

5.  Adding to point 4:  water consumes tremendous energy as it evaporates.  Therefore, sweating cools the body very effectively, guarding against overheating.

6.  Water functions as a lubricant in the body.  In saliva it helps the food move easily down the esophagus.  In synovial fluid it lubricates the knee joint.

Sources:

Inquiry into LIfe, 11th edition, by Sylvia S. Mader.  McGraw-Hill:  2006.

Biology 12, Module 1:  Cell Biology 1.  Open School BC:  2007.