Principles of Biochemistry

1.1.3.5 Mitochondrion

Mitochondrion is spherical to rod-shaped organelle with a double membrane. The inner membrane is infolded many times, forming a series of projections (called cristae).The space between the two membranes is called “outer chamber” or “inter membrane space”. It is filled, with a watery fluid and is 40-70Ǻ in width. The space bounded by inner membrane is called the “inner chamber” or “inner membrane space”. The inner membrane space is filled with a matrix. It is rich in enzymes and contains dense granules, ribosomes, and mitochondrial DNA.  The granule consists of insoluble inorganic salts and are believed to be the binding sites of bivalent ions like Mg²⁺ and Ca²⁺. The side of the inner membrane facing the matrix side is called M-side, while the side facing the outer chamber is called C-side. Two to six circular DNA molecules have been identified within mitochondria. They may be present free in the matrix or may be attached to the membrane. The enzymes of the Krebs cycle are located in the matrix.In general the outer membrane contains more proteins and phospholipids than the inner membrane. Phosphatidylcholie is the predominant lipid of the outer membrane.The innermembrane on the other hand contains most of the diphophatidylglycerol. On the inner layer of cristae are found stalked particles or repeating triparticle units which are sometimes called respiratory assemblies. Each stalked particles or repeatng triparticle units which are sometimes consists of  abase, a stalk spherical head. The spherical soluble coupling particle called F₁ particle which is actually the enzyme ATPase, oxidative phosphorylation takes place on stalked particles. Mitochondria convert the energy stored in glucose into ATP (adenosine triphosphate) for the cell and hence are the power house of the cell.