Biology » Introducing the Cell » Cell Organelles



A mitochondrion is a membrane bound organelle found in eukaryotic cells. This organelle generates the cell’s supply of chemical energy by releasing energy stored in molecules from food and using it to produce ATP (adenosine triphosphate). ATP is a special type of “energy carrying” molecule.

Structure and function of the mitochondrion

Mitochondria contain two phospholipid bilayers: there is an outer membrane, and in inner membrane. The inner membrane contains many folds called cristae which contain specialised membrane proteins that enable the mitochondria to synthesise ATP. Inside the inner membrane is a jelly-like matrix. Listed from the outermost layer to the innermost compartment, the compartments of the mitochondrion, are:

  • Outer mitochondrial membrane
  • Intermembrane space
  • Inner mitochondrial membrane
  • Cristae (folds of the inner membrane)
  • matrix (jelly-like substance within the inner membrane)
Schematic DiagramMicrograph

The table below relates each structure to its function.

StructureFunctionAdaptation to function
Outer mitochondrial membraneTransfer of nutrients (e.g lipids) to mitochondrionHas large number of channels to facilitate transfer of molecules
Intermembrane spaceStores large proteins allowing for cellular respirationIts position between two selectively permeable membranes allows it to have a unique composition compared to the cytoplasm and the matrix
Inner membraneStores membrane proteins that allow for energy productionContains folds known as cristae which provide increased surface area, thus enabling production of ATP (chemical potential energy)
MatrixContains enzymes that allow for the production of ATP (energy)The matrix is contains a high quantity of protein enzymes which allow for ATP production


In Life Sciences it is important to note that whenever a structure has an increased surface area, there is an increase in the functioning of that structure.

Video: Mitochondria Powering the Cell

Together Harvard University and XVIVO developed the 3D animation journey below for Harvard’s undergraduate Molecular and Cellular Biology students about the microscopic world of mitochondria. The animation highlights the creation of Adenosine Triphosphate (ATP) — mobile molecules which store chemical energy derived from the breakdown of carbon-based food.

ATP molecules act as a kind of currency, imparting chemical energy to power all the functional components of cellular activity. This piece is the second in a series of award winning animations XVIVO is creating for Harvard’s educational website BioVisions at Harvard. The first program, Inner Life of the Cell, received international acclaim and can be seen both on our website and the BioVisions site.

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