ATP

• adenosine triphosphate
• ATP is synthesised when energy is made available (in the mitochondria) and is broken down when energy is needed such as in muscle contraction
• when energy is needed in organisms the enzyme ATPase hydrolyses the bond between the second and third phosphate groups - leaving only two
• ATP molecule is hydrolysed into adenosine diphosphate - ADP - and an inorganic ion, this reaction is reversible
• ATP transfers free energy from energy rich compounds like glucose to cellular reactions but some energy is lost as heat energy
• the hydrolysis of ATP into ADP involves a single reaction and releases energy immediately but glucose involves many intermediates
• only one enzyme is needed to release energy from ATP but many are needed to release it from glucose
• ATP releases energy in small amounts where it is needed but glucose contains large amount of energy and releases it all at once
• ATP is used to in metabolic processes - to build large complex molecules like DNA from smaller simpler molecules like nucleotides
• ATP is used in active transport
• ATP is used in muscle contraction
• ATP is used in secretion - the packing and transport of secretory products into vesicles in cells