Why is polarity important in living things?

Answer 1

Many peculiar properties of water depends on the fact that the water molecule is polar.

The specific water behavior depends on the fact that one water molecule establish the so called hydrogen bond, possible due to polarity, with four nearby molecules . In particular the oxygen atom is bonded with two hydrogen atoms of other molecules, while the two hydrogen atoms are bonded to other two molecules at the oxygen terminal. This due to the residual positive charge of the hydrogen part and negative residual charge of the oxygen.

This set of weak bonds causes, for example, the fact that, at atmospheric pressure , water density is at maximum at 4 °C when water is liquid while the density of ice (solid water) is greater.

Moreover, the polarity of water renders it a very good solvent. As a matter of fact, when another polar material enters in water, water molecules substitute the polar bonds maintaining the material in solid state surrounding the atoms or the molecules with a water molecules layer (called hydration layer) so to decrease the energy of the solution and render it stable.

Last, but not least, the water polarity causes that hydroxyl and hydrogen ions move in water when an electrical field is present (during electrophoresis) by exchanging electrons with water molecules more than by simple push of the electrical field, having much higher mobility with respect to other ions.

Answer 2

Polarity is the main contributor when considering the solubility of molecules in solvents. Water has many important properties, and its polarity is one of them. Water's polarity allows many molecules to exist as solutes in a solution (water being the solvent). This allows life to have a common medium where many of the reactions essential for life are allowed to take place.

Polarity is also responsible for the ability of membranes to protect cells. The polar "heads" assosiate with the outside and inside of the cell. The inner "tails" are hydrophobic and do not allow any polar or charged molecules through (because they are not soluble in a hydrophic environment; hence it is energetically unfavorable to pass through this area as a polar molecule) without assistance (like with a protein).

Answer 3

Water is considered as the universal solvent. Its polarity of water allows it to dissolve substances that are needed for various biochemical reactions.