In which organelles the cell is breathing.

Mitochondria are rod-like organelles that can be thought of as the cell’s energy generators that convert oxygen and nutrients into adenosine triphosphate (ATP). ATP is the “currency” of the cell’s chemical energy, which fuels the metabolic activities of the cell. This process is called aerobic respiration and is the reason animals breathe oxygen. Without mitochondria, higher animals probably won’t exist, because their cells will be able to get energy from anaerobic respiration (in the absence of oxygen), a process much less efficient than aerobic respiration. In fact, mitochondria allow cells to produce 15 times more ATP, and higher animals need a lot of energy to survive.