Final answer:
The sugar in an ATP molecule is ribose, and ATP serves as the primary energy currency of the cell, transferring and storing energy through its three phosphate groups.
Step-by-step explanation:
The three parts of an ATP molecule are adenine, phosphate units, and the sugar known as ribose. Adenosine triphosphate or ATP is commonly referred to as the energy currency of the cell, as it stores and transfers energy within cells.
ATP is composed of the purine base adenine, which is attached to the five-carbon sugar ribose, and is bonded with three phosphate groups. These phosphate groups, particularly the bond between the second and third phosphate (anhydride linkage), store a significant amount of potential energy, which is released during hydrolysis to fuel various cellular activities such as muscle contraction and the transport of substances across cell membranes.