Cellular respiration takes place in the mitochondria. This is where the chemical energy of glucose, carbohydrates, fats and proteins is harvested and partially captured in the form of ATP. Cellular respiration involves glycolysis, the Krebs cycle and oxidative phosphorylation via the electron transport chain. Glycolysis occurs in the cytosol, and the other two processes occur in the mitochondria. In the absence of oxygen, respiration is confined to the cytosol.
An organelle is a component of the cell, such as the mitochondria, that has its own DNA. These entities evolved from independent organisms and eventually became part of the human cell. The mitochondria are referred to as cellular power plants because they generate most of the ATP the cells need for energy. In addition, mitochondria are involved with signaling, differentiation of cells and cellular growth and death.
Mitochondria have also been implicated in diseases such as cardiac dysfunction and autism as well as the aging process. These organelles are composed of particles that perform different functions. While most of human DNA is contained in the nucleus of a cell, mitochondrial DNA resembles the bacterial genome. Most eukaryotic cells, which are found in plants, animals, fungi and other life forms, contain mitochondria.