Final answer:
Mitochondria are the cell organelles that convert fuel particles into usable energy by producing ATP through cellular respiration, using oxygen and releasing carbon dioxide as a byproduct.
Step-by-step explanation:
The cell organelle that converts fuel particles into usable energy is the mitochondrion (mitochondria, plural). These organelles are often described as the "powerhouses" or "energy factories" of the cell. They are responsible for carrying out cellular respiration, a process that transforms the chemical energy found in nutrients like glucose into adenosine triphosphate (ATP), which is the main energy-carrying molecule used by cells. The mitochondria use oxygen in this process and produce carbon dioxide as a waste product, which you exhale with every breath.