What is Mitochondria in Biological Sciences

Mitochondria were first observed by “Altmann” in 1894 who described as “bioblasts”. Benda (1897) called them “mitochondria”. (mitoG =thread; chondrionG=granule). The number of mitochondria varies with the cell type and functional stages. In eukaryotes, approximately 2000 mitochondrias occupies one-fifth of its total cell volume. The mitochondrial chemical composition is concerned, mitochondria consist of 65-70% proteins, 25-30% lipids, 5-7% DNA and 0.5% RNA. The4 outer membrane of the mitochondria has “porins”, which permits molecules up to 10kd. Matrix is gel like solution, containing high concentration of soluble enzymes, substrate, nucleotide cofactors, ions.


  •  1880 – Kolliker – observed in muscle cells of insects
  • 1882 – Flemming- gave the name as “fila”
  • 1894 – Altamann- gave systematic name observation name as “Bioblast”
  • 1897-98 – Benda- gave name as “Mitochondria”. He stained the mitochondria with “alizarin” and “crystal violet”.
  • 1900 – Michaelis- stained mitochondria with “jaunus green”
  • 1934 – Bensley & Hoperr – said mitochondria is the site for the cellular respiration.


  • Fuchsinophilic granules,
  • Parabasal bodies,
  • Plasmosomes,
  • Fila,
  • Chondriosomes,
  • Vernicules
  • Bioblasts.


The mitochondrion is a sub cellular organelle having the outer and inner membranes enclosing the matrix. The inner membrane is highly selective in its permeably characteristics. The inner membrane contains the respiratory chain and translocating systems. The knobs like protrusions represent the ATP synthase system. The inner membrane is folded into a series of internal ridges called “Cristae”, which may be longitudinally or transversely oriented, branched or tabular. Hence, there are two compartments in mitochondria: the intermembrane space between the outer and inner membranes and the matrix, which is bounded by the inner membrane. Most of the reactions of the TCA cycle and fatty acid oxidation occur in the matrix. For more information wikipedia is the good source for mitochondria

What is Mitochondria in Biology


localization of some enzymes in rat Liver Mitochondria:

Outer membrane

  • Monoamine oxidase
  • Kynurenine-3-monoxygenase
  • NADH dehydrogenase
  • CoA Synthetase4
  • Phospholipase-A2
  • Nucleoside diphosphate kinase

 Inner membrane:

  • NADPH dehydrogenase
  • Iron-Sulfur proteins
  • b,c,c1and aa3
  • F1 ATPase
  • Succinate dehydrogenase
  • Carnitine acyl transferase


  • TCA Cycle enzymes
  • Fatty acyl-CoA oxidation enzyme

Space between the membranes:

  • Adenylate kenase
  • Creatine Kinase

Functions of mitochondria:

The mitochondria are organelles which transfer the chemical energy of the metabolites of the cell (through Krebs cycle and the respiratory chain.) into the high-energy phosphate bond of ATP. Thus, mitochondria are the “power house of the cell”, that produce the energy necessary for many vital cellular functions via, motility contraction (muscle contraction), biosynthesis of cell bioluminescence etc.

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  • Updated December 2, 2015
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