Scientist believe that about 25 of the known elements are essential to life. Just four of these - Carbon (C), Oxygen (O), Hydrogen (H), and Nitrogen (N), - make up about 96% of the human body.
These four elements are found in the basic structure of all biochemical molecules. For example, Glucose is a carbohydrate and it's molecular formula is C6H12O6 - each molecule of glucose is made up of 6 Carbon atoms, 12 Hydrogen atoms and 6 oxygen atoms.
The other elements found can be divided into two main groups - major elements and trace elements.
The human body functions as a result of a large number of the chemical reactions involving compounds of a of these elements.
