Water
Water is the most abundant and important inorganic compound in living material. Water makes up 60% to 80% of the volume of most living cells. Five important properties of water are:
1) High heat capacity- water absorbs and releases large amounts of heat before changing appreciably in temperature preventing sudden changes in temperature caused by external factors. As part of blood, water redistributes heat among body tissues, ensuring temperature homeostasis.
2) High heat of vaporization- When water vaporizes or evaporates it changes from liquid to gas. This requires large amounts of heat to be absorbed to break the hydrogen bonds that hold water molecules together. This is extremely beneficial when humans sweat.
3) Polar solvent properties- Water is an unparalleled solvent. Water molecules orient themselves with their slightly negative ends toward the positive ends of the solutes, and vice versa, first attracting them, then surrounding them. This explains why ionic compounds and other small reactive molecules dissociate in water. Water also forms hydration layers around large charged molecules such as proteins. Water is the body's major transport medium because it has an excellent solvent.
4) Reactivity- Water is an important reactant in many chemical reactions. In hydrolysis reactions are foods digested to their building blocks by adding a water molecule to each bond to be broken. In dehydration synthesis, large carbohydrates or protein molecules are synthesized from smaller molecules, a water molecule is removed for every bond formed.
5) Cushioning - By forming a resilient cushion around certain body oregans, water helps protect them from physical trauma. The cerebrospinal fluid surrounding the brain exemplifies water's cushioning role.

Salt
A salt is an ionic compound containing cations other than H+ and anions other than the hydroxyl ion (OH-). All ions are electrolytes, substances that conduct an electrical current in solution. When salts dissolve in water, they dissociate into their component ions. Salts commonly in the bod include sodium chloride, calcium carbonate and potassium chloride. In an ionized form, salts play vital roles in body function. For example the most beneficial salts make bones and teeth hard.

18) The Importance of Water and Salt