What are mitochondria?

We explain what mitochondria are and the origin of these organelles. In addition, its main functions and how is its structure.

  1. What are mitochondria?

Mitochondria  are the cytoplasmic organelles (that is: cell equivalents to the body’s organs) that in cells operate as energy plants, synthesizing the adenosine triphosphate ( ATP ) molecules that provide chemical fuel to the various cellular processes necessary for life (respiration mobile).

This process of energy synthesis is carried out inside the cell, taking advantage of glucose, fatty acids and amino acids as fuel, which enter the mitochondria through the membranes that cover them, similar but smaller in size. cell membrane .

Commonly, these organelles have an elongated , although highly variable, appearance and are found in the cell cytoplasm , in a number according to the energy needs of the type of cell in question.

  1. The origin of mitochondria

The curious thing about mitochondria is that they have in their own DNA the necessary instructions to synthesize the essential energy substances and to replicate themselves during cell reproduction . This DNA is not identical to that of the cell nucleus, which has allowed us to formulate a hypothesis regarding its origin: endosymbiosis.

According to this theory, the mitochondria  would have arisen as a result of the symbiotic (collaborative) incorporation of a prokaryotic into the eukaryotic cell , reaching a kind of coexistence agreement that later became indispensable: the prokaryote would produce energy for the whole cell and in return It would be protected inside, a nutrient-rich and competition-free environment. The rest would be the evolution, which would end up merging them both in the same organism.

The clues that support this theory have to do with the presence of   autonomous DNA and its own plasma membrane in the mitochondria, as well as its physical, biochemical and metabolic similarity with numerous bacteria.

  1. Mitochondria function

Mitochondria serve as a storehouse for ions, water molecules and proteins.

As said, mitochondria are responsible for producing chemical energy for the entire cell , from the synthesis of ATP. To do this, it must oxidize metabolites by oxidative phosphorylation, generating a very high percentage of the energy produced by the cell.

At the same time, mitochondria serve as a storehouse for ions, water molecules and proteins , often captured from the cytoplasm to serve as spare parts in the synthesis of energy.

  1. How is its structure?

The spaces of the mitochondria are covered by a double lipid membrane.

The structure of the mitochondria is variable , but usually it is composed of three different spaces: mitochondrial ridges, intermembrane space and mitochondrial matrix, all covered by a double lipid membrane, similar to the cell membrane, but mostly composed (60 to 70% in the external, 80% in the internal) protein.

  • Mitochondrial crests . It is a system of crests or folds, which connects with the mitochondrial membranes from time to time, thus allowing the transport of materials inside the organelle and exerting specific enzymatic (catalytic) functions.
  • Intermembranous space  . Between the two mitochondrial membranes there is a space rich in protons (H +) resulting from the enzymatic complexes of cellular respiration, as well as the molecules responsible for transporting fatty acids into the mitochondria, where they will proceed to oxidation.
  • Mitochondrial matrix . Also called mitosol, it contains ions, metabolites to oxidize, double-stranded circular DNA molecules (very similar to bacterial DNA), ribosomes, mitochondrial RNA and everything necessary for the synthesis of ATP. There the Krebs cycle and the beta-oxidation of fatty acids take place, as well as reactions of urea synthesis and heme groups, all of which generate a significant amount of chemical energy that is then released to the cell cytoplasm.

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