ATP

• Adenosine triphosphate (ATP) is the universal energy supplier in cells
• ATP is a nucleotide with three phosphate groups attached

  
• It is the energy in the phosphate bonds of ATP,

  particularly the end one, that is made available to cells to use to make or break bonds.
• When energy is needed, the third phosphate bond can be broken by a hydrolysis reaction, which is catalysed by the enzyme ATPase. The result is adenosine diphosphate (ADP), a free organic phosphate group (Pi) and energy. Some of this energy is lost as heat and is wasted. The test is used for any biological activity which requires energy e.g. active transport
• adenosine triphosphate + H2O ⇌ adenosine diphosphate + Pi
• the energy needed to drive the synthesis of ATP comes from catabolic (breakdown) reactions or redox reactions.
• An ATP molecule provides an immediate supply of energy for the cells, ready to use when needed.
• ATP is made in a condensation reaction
• Energy is released in catabolic reactions such as cellular respiration
• The main way energy is released is by the removal of hydrogen atoms from several intermediate compounds in a metabolic pathway. When two hydrogen atoms are removed from a compound, they are collected by a hydrogen carrier or acceptor that is reduced. Electrons from the hydrogen atoms are then transferred along a series of carriers known as electron transport chain. The components of the chain are reduced when they receive the electrons, and oxidized again when they transfer the electrons. These redox reactions release a small amount of energy which is used to drive the synthesis of ATP