Cellular respiration is the process by which a living cell produces adenosine triphosphate (ATP), carbon dioxide, and water from oxygen and organic fuel. It is a catabolic pathway that involves the release of stored energy from the break down of complex molecules to more simple ones. No single chemical reaction covers the entire process of cellular respiration. Instead it is the cumulative function of glycolysis, the Krebs cycle and electron transport. In eukaryotes, the mitochondria is the primary organelle that contains the enzymes that drive cellular respiration.

Nearly all eukaryotic cells contain some mitochondria. While there may be as few as one mitochondria in a cell, often there are hundreds or thousands. The number typically depends on the metabolic activity of the cell. The mitochondria is enclosed in a two membrane envelope in which a variety of proteins are embedded. Inside these membranes is the mitochondrial...