The mitochondrion is a eukaryotic cell organelle.
Structure of the mitochondrion
It is now accepted that the mitochondrion develops by endocytosis of a bacterium by an ancestral cell (endosymbotic theory). The mitochondrion has a DNA genome in a circular chromosome, the genes of which resemble those carried by bacteria.
The mitochondrion is an oval-shaped organelle, delineated from the cytoplasm by two superimposed membranes:
- an exposed membrane, containing many porins (canal-shaped proteins) allowing molecules to pass through;
- and an internal membrane, folded in order to create numerous invaginations which increase the surface area of the membrane without increasing the volume of the mitochondrion. This is the membrane on which the cell respiration engines are located.
Role of the mitochondrion
The mitochondrion is the place where cellular respiration takes place, or it is the cell's energy factory. It converts glucose into the energy molecule ATP, via ATP synthetase enzymes. This process takes place during the "Krebs cycle", a set of metabolic reactions that take place in the mitochondrion.
Diagrammatic representation of mitochondrial structure: 1: internal membrane; 2: external membrane; 3: intermembrane space; 4:matrix. © Tatoute, Wikimedia, CC by-sa 3.0