Final answer:
ATP is the energy currency used by cells, produced during processes such as glycolysis and the Krebs cycle, and is essential for energy transfer within the cell.
Step-by-step explanation:
The energy currency used by cells is ATP (adenosine triphosphate). This molecule is crucial for storing and transferring energy within cells. ATP is produced during various metabolic processes including glycolysis, where glucose is split into two molecules of pyruvate, and during the Krebs cycle, where FADH2 is produced. Additionally, aerobic cellular respiration results in the production of ATP and H₂O. Among the molecules that can store potential energy, glucose is likely to have the most, even more than ATP or sucrose, due to its various energy-rich bonds.
During photosynthesis, it's the molecule chlorophyll that absorbs the energy of a photon, not ATP or glucose. Finally, ATP is considered the energy currency of the cell because it can be easily used to transfer energy from one reaction to another, facilitating various cellular functions.