One of the major features distinguishing prokaryotes from eukaryotes is the presence of mitochondria. Mitochondria are constantly referred to as “the powerhouse of the cell” because they produce adenosine triphosphate (ATP), the cell’s main energy-carrying molecule.

Mitochondria are double-membrane organelles that contain their ribosomes and DNA. Each membrane is a phospholipid bilayer embedded with proteins. The mitochondrial inner membrane is extensive and involves substantial infoldings called cristae. The space between the membranes is called the intermembrane space, and the compartment enclosed by the inner membrane is called the mitochondrial matrix. The matrix contains mitochondrial DNA and ribosomes. Because of this, the mitochondria are also self-replicating.

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Key Points

• Mitochondria contain their ribosomes and DNA and have a double membrane.

• Mitochondria have an important role in cellular respiration through the production of ATP.

• The mitochondria are self-replicating.

Key Terms

Mitochondria: “powerhouse of the cell”, make ATP

Adenosine triphosphate (ATP): cell’s main energy-carrying molecule

Cristae: foldings in the mitochondrial inner membrane

Intermembrane space: space between the outer and inner membrane of the mitochondria

Matrix: space enclosed by inner membrane of mitochondria, contains mitochondria DNA and ribosomes

Ribosomes: made of RNA and produce proteins

Phospholipid bilayer: consists of two layers of phospholipids, with a hydrophobic, or water-hating, interior and a hydrophilic, or water-loving, exterior

Mitochondrial DNA: the small circular chromosome found inside mitochondria