We explain what mitochondria are and the origin of these organelles. Also, its main functions and what its structure is like.
What are mitochondria?
The mitochondria are the cytoplasmic organelles (that is, cellular equivalents to the body's organs) that in cells operate as energy plants, synthesizing adenosine triphosphate (ATP) molecules that provide chemical fuel to the various cellular processes necessary for life (cellular respiration).
This energy synthesis process takes place inside the cell, using glucose, fatty acids and amino acids as fuel, which enter the mitochondria through the membranes that cover them, similar, although smaller in size, to the cell membrane.
Commonly, these organelles have an elongated appearance although extremely variable, and is found in the cell cytoplasm, in a number according to the energy needs of the type of cell in question.
See also: Plant cell
The origin of mitochondria
The curious thing about mitochondria is that they have in their own DNA the necessary instructions to synthesize essential energy substances and to replicate themselves during cellular 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, mitochondria would have arisen as a result of symbiotic incorporation (collaborative) of a prokaryote within the eukaryotic cell, reaching a kind of coexistence agreement that later became indispensable: the prokaryote would produce energy for the entire cell and in exchange would be protected inside, a medium rich in nutrients and free of competence. The rest would be done by evolution, which would end up merging them both into 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 to numerous bacteria.
Function of mitochondria
As mentioned, mitochondria are responsible for producing chemical energy for the cell all, from the synthesis of ATP. To do this, it must oxidize metabolites through oxidative phosphorylation, generating a very high percentage of the energy produced by the cell.
At the same time, the mitochondria serve as a store for ions, water molecules and proteins often captured from the cytoplasm to serve as spare parts in the synthesis of energy.
What is its structure like?
The structure of the mitochondria is variable but it is generally composed of three different spaces: mitochondrial cristae, intermembranous 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) of proteins.
- Mitochondrial ridges It is a system of crests or folds, which connects with the mitochondrial membranes from time to time, thus allowing the transport of materials into the organelle and exercising specific enzymatic (catalyzing) 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 be oxidized.
- 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 beta-oxidation of fatty acids take place, as well as urea and heme group synthesis reactions, all of which generate a significant amount of chemical energy that is then released into the cell cytoplasm.
