ATP

• All living organisms require energy to survive. For example, plants use solar energy to combine water and carbon dioxide into complex organic molecules via photosynthesis. Both plants and animals then oxidise these organic molecules to make adenosine triphosphate (ATP), which is used as an energy source within cells.
• ATP is a phosphorylated macromolecule made up of three elements - adenine (nitrogenous organic base), ribose (5 carbon sugar) and 3 phosphate groups.
• ATP contains three phosphate groups, and the bonds between these phosphate groups are unstable, therefore have low activation energy. This means that they are easily broken, and release a considerable amount of energy when they do.
• The symbol equation for the hydrolysis of ATP is : ATP + (H2O) -> ADP + Pi + energy.
• The word equation for the hydrolysis of ATP is : adenosine triphosphate + water -> adenosine biphosphate + inorganic phosphate + energy.
• As water is used to convert ATP into ADP, this is known as a hydrolysis reaction. This reaction is catalysed by the ATP hydrolase enzyme.