The organelle responsible for releasing energy stored in food is the mitochondrion.

Here's why:

* Cellular Respiration: Mitochondria are the powerhouses of the cell, where cellular respiration takes place. Cellular respiration is the process of breaking down glucose (a sugar) in the presence of oxygen to release energy in the form of ATP (adenosine triphosphate).

* ATP Production: ATP is the primary energy currency of cells. Mitochondria are crucial for producing ATP, which fuels all cellular processes.

Let me know if you'd like to know more about cellular respiration or mitochondria!