Final answer:
Mitochondria are membrane-enclosed organelles found in eukaryotic cells, responsible for generating most of the cell's ATP. They are often referred to as the "powerhouses" or "energy factories" of the cell. Cellular respiration occurs in mitochondria, converting energy from nutrient molecules into ATP.
Step-by-step explanation:
Mitochondria are membrane-enclosed organelles found in eukaryotic cells that generate most of the cell's ATP. Mitochondria are often called the "powerhouses" or "energy factories" of the cell because they are responsible for making adenosine triphosphate (ATP), the cell's main energy-carrying molecule. Cellular respiration, which takes place in mitochondria, converts energy stored in nutrient molecules into ATP.