The structures that convert nutrients to energy are primarily mitochondria, often referred to as the "powerhouses" of the cell.

Here's a breakdown:

* Mitochondria: These organelles are responsible for cellular respiration, the process where glucose (a sugar) is broken down in the presence of oxygen to produce ATP (adenosine triphosphate). ATP is the primary energy currency of cells.

* Other Structures: While mitochondria are the central players, other structures contribute to the energy conversion process:

* Digestive System: Breaks down food into smaller molecules that can be absorbed.

* Small Intestine: Absorbs nutrients like glucose and amino acids.

* Cytoplasm: Contains enzymes necessary for glycolysis, the initial stage of glucose breakdown.

In summary: Mitochondria are the primary structures responsible for converting nutrients into energy, but the process involves the coordinated actions of various cellular components and systems within the body.