Paul Andersen explains the structure, function and importance of adenosine triphosphate (ATP). He begins by describing the specific structure of the molecule and its three main parts: adenine, ribose sugar, and phosphate groups. He explains how energy can be stored in ATP and released through hydrolysis to ADP and Pi. He shows how the molecule is created in cellular respiration and photosynthesis. He also explains how it is used throughout the cell. He finishes with a brief discussion of LUCA and how elements of ATP can be found in other parts of the cell (including RNA, DNA).