Membrane-shaped organoids found in all eukaryotic cells. Mitochondria are responsible for aerobic respiration , so their number per cell is very variable, and is generally higher in those with higher metabolic activity. It is denominated chondrioma the set of mitochondria of a cell.

Although visible under an optical microscope, its ultrastructure only became known after the advent of electron microscopy, under which they show to be formed by two lipoproteic membranes.

Structure of mitochondria

The mitochondria are coated with a double membrane, one external , smooth and continuous, and one internal , with folds called mitochondrial ridges .

In these crests, are structures rich in enzymes , denominated elementary particles, important for the stages of cellular respiration. Like chloroplasts, they present DNA, RNA and their own ribosomes (mitorribosomos), being able to autoduplicate and to synthesize part of their proteins.

This situation is evidence that mitochondria could have been independent organisms, removing directly from the environment the molecules they needed for their own metabolism.


The function of mitochondria, then, is to produce energy in the form of ATP for the cell to perform its metabolic processes. This production of energy occurs through a phenomenon called cellular respiration .

Its activities are compartmentalized: the set of reactions called the Krebs cycle occurs in the mitochondrial matrix,  glycolysis occurs in hyaloplasm and comprises a sequence of chemical reactions similar to those that occur in the fermentation, while the respiratory chain reactions responsible for oxidative phosphorylation occur in the mitochondrial crests.


The high degree of independence of mitochondria and chloroplasts, due to the fact that they have their own nucleic acid molecules (DNA and RNA), led to the elaboration of the ” endosymbiotic hypothesis ” about the origin of life : these organelles originated from prokaryotes free life, possibly bacteria that at some point were associated with a eukaryotic cell.

In the process of fecundation, only the mitochondria of the female gamete are multiplied in the embryo cells, therefore, the mitochondrial DNA is a maternal inheritance, serving as an instrument for the determination of parental relationships in genomic tests.

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