02.04 Molecules

A combination of different atoms makes up a molecule which is held together by chemical bonds e.g. each water molecule (H2O) is made of two hydrogen (H) atoms and one oxygen (O) atom (Figure 2.3).

Our body is made up of two main groups of molecules - organic and inorganic. Inorganic molecules are typically small structures and contain little or no carbon (C). The two most important inorganiccompounds in our body are water and salts e.g. NaCl (common salt). Organic molecules are larger and more complex and contain carbon. These molecules have important structural and functionalproperties. The major classes of organic molecules found in t h e human body are lipids (fats), carbohydrates (sugars), proteins and nucleic acids. The nucleic acids, better known as DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) carry all our genetic material in the form of genes.

Figure 2.3 A water molecule is made up of two hydrogen (H) atoms and one oxygen (O) atom (Copyright, QUT)