Final answer:
After an ATP molecule loses a phosphate group, ADP (adenosine diphosphate) and an inorganic phosphate are formed, releasing energy used by the cell. This process is termed dephosphorylation. ATP acts as energy currency, and by losing a phosphate group, it powers cellular functions.
Step-by-step explanation:
When an ATP (adenosine triphosphate) molecule loses a phosphate group, the result is the formation of ADP (adenosine diphosphate) and an inorganic phosphate (Pi). This process is known as dephosphorylation and it releases energy that the cell can use for various functions.
The bonds between the phosphate groups in ATP are considered high-energy because a lot of energy is stored in the repulsion between the negatively charged phosphate groups. Therefore, when one phosphate is removed, usually through a hydrolysis reaction that adds a water molecule (H2O), the energy that was used to maintain the bond is released for the cell to use in other processes. Adenosine monophosphate (AMP) can also be produced from ATP by removing two phosphates instead of just one.
The energy released from ATP hydrolysis is often used to drive other chemical reactions within the cell, which are called endergonic reactions. Therefore, ATP can be thought of as a sort of energy currency for the cell, storing and providing energy as needed. If a cell needs to store energy again, it can reattach a phosphate to ADP to recreate ATP, in a process known as phosphorylation - analogous to recharging a battery.