Final answer:
The energy currency used by cells is ATP (adenosine triphosphate), a molecule that transfers energy within the cell to power various processes. Option a is correct.
Step-by-step explanation:
The energy currency used by cells is adenosine triphosphate (ATP). This molecule is essential in transferring energy from energy-yielding processes, like the breakdown of glucose, to energy-requiring cellular processes. ATP is composed of a ribose sugar, an adenine base, and three phosphate groups.
The bonds between these phosphate groups store potential energy that, when broken, release energy that the cell can use to perform various functions. During the process called glycolysis, glucose is catabolized to produce ATP, which then serves as immediate fuel for cellular activities.
When a cell requires energy, ATP undergoes hydrolysis, removing one of its phosphate groups and releasing energy; this transforms ATP into adenosine diphosphate (ADP). Cells continuously regenerate ATP from ADP by using energy derived from the catabolism of nutrients like glucose.