IV.

Water in Life

Water is the major constitutent of living matter. From 50 to 90 percent of the weight of living organisms is water. Protoplasm, the basic material of living cells, consists of a solution in water of fats, carbohydrates, proteins, salts, and similar chemicals. Water acts as a solvent, transporting, combining, and chemically breaking down these substances. Blood in animals and sap in plants consist largely of water and serve to transport food and remove waste material. Water also plays a key role in the metabolic breakdown of such essential molecules as proteins and carbohydrates. This process, called hydrolysis, goes on continually in living cells.