Inorganic compounds include water, sodium chloride, potassium hydroxide and calcium phosphate.
Water is the most abundant inorganic compound, making up over 60% of the volume of cells and over 90% of body fluids like blood. Many substances dissolve in water and all the chemical reactions that take place in the body do so when dissolved in water. Other inorganic molecules help keep the acid/base balance ( pH) and concentration of the blood and other body fluids stable (see Chapter 8).
Organic compounds include carbohydrates, proteins and fats or lipids. All organic molecules contain carbon atoms and they tend to be larger and more complex molecules than inorganic ones. This is largely because each carbon atom can link with four other atoms. Organic compounds can therefore consist of from one to many thousands of carbon atoms joined to form chains, branched chains and rings (see diagram below). All organic compounds also contain hydrogen and they may also contain other elements.