 The water molecule is a polar molecule, meaning it has a partial positive end and partial negative end.

 Because water is polar, it has the ability to hydrogen bond with itself. The (-) oxygen ends attract the (+) hydrogen ends.  Hydrogen bonds are weak bonds between the molecules.  Hydrogen bonds are used between cellular molecules to hold structures and function, but can be easily broken. (ex: DNA nucleotides)

 High Heat Capacity- requires a lot of energy to raise the temperature of 1g of water by 1 ◦ C. (1 calorie or 4.18 Joules)  This is important to living things because it helps maintain a steady body temperature.  High Heat of Evaporation- 540 calories are required to evaporate 1 g of water.  This helps animals release excess body heat (sweat)

 Water is said to be the universal solvent.  Because of it’s polarity, water can dissolve a large number of solutes, like salt.  Since water molecules can adhere to one another and other substances, it can transport nutrients and waste throughout the body.  Hydrophobic substances- “water fearing” These don’t attract to water  Hydrophilic substances- “water loving” these substances do attract to water. This is important for the phospholipids in our plasma membrane.

 Acids produce Hydrogen Ions (H + )  Bases produces Hydroxide Ions (OH - )  The strength or weakness of an acid or base depends on how well it dissociates in water.  Acids have a high [H + ]  Bases have a high [OH - ]

 pH scale  Ranges from 0 to 14 and indicates the [H + ].  Acids range from 0 to <7.  Bases range from >7 to 14.  Neutral solutions have a pH of 7 and [H + ]=[OH - ]

 Buffers- chemicals that keep the pH within normal limits  Our bodies rely on buffers to keep body fluids within a narrow range, otherwise our molecules would not function properly.  Our blood pH is 7.4. If it drops below 7 or rises above 7.8, life threatening conditions can occur.

 Buffer used in our blood is bicarbonate.