1. Oxygen and Carbon Dioxide
Inorganic molecules do not contain carbon and
were not synthesised from a biological origin
(oxides of carbon and carbonates are
exceptions)
Certain inorganic molecules play important
roles in maintaing living organisms

2. Minerals
Mineral nutrients are the chemical elements required by
living things other than the four main elements of organic
molecules (C, H, O, N)
Phosphorus is a part of nucleic acids, cell membranes and ATP
Sulphur is found in certain amino acids and can play an
important role in the structure and function of proteins
Calcium is important in the growth and development of bones
and teeth
Sodium and potassium are involved in neuronal signalling
(nervous communication)
Iron is found in red blood cells and is necessary for the transport
of oxygen in blood
Magnesium is found in chlorophyll, which is required for
photosynthesis

3. Structure of a Water Molecule:
• Water (H2O) is made up of two hydrogen atoms
covalently bound to an oxygen atom
• While this bonding involves the sharing of
electrons, they are not shared equally
• The oxygen atom, having more protons
(+ve), attract the electrons (-ve) more strongly (i.e.
the oxygen has a higher electronegativity)
• Thus the oxygen atom becomes slightly negative
and the hydrogen atoms become slightly positive