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Mitochondrial Structure and Function
Mitochondria are immersed in the cytosol between the various sacs and filaments that fill the cytoplasm of eukaryotic cells.
They are true “powerhouses” of cells because produce energy for all cellular activities.
Mitochondria were discovered in the mid-nineteenth century, and for decades their existence was questioned by some cytologists. Only in 1890, the presence of mitochondria in the cellular cytoplasm was indisputably demonstrated. The term “mitochondria” (from Greek, mythswire and condros, cartilage) appeared in 1898, possibly as a reference to the filamentous and homogeneous (cartilaginous) appearance of these organelles in some cell types when viewed under the light microscope.
Mitochondria, ranging in number from tens to hundreds, depending on cell type, are present in practically all eukaryotes, whether animals, plants, algae, fungi or protozoa.
Internal structure of mitochondria
Mitochondria are delimited by two lipoprotein membranes similar to other cell membranes. While the outer membrane is smooth, The inner membrane has numerous folds - mitochondrial ridges - protruding into the organelle.
The inner cavity of the mitochondria is filled by a fluid called mitochondrial matrix, where several enzymes are present, as well as DNA and RNA, and small ribosomes and substances needed to make certain proteins.
The cellular respiration
Within the mitochondria occurs cellular respiration, a process in which organic food molecules react with oxygen gas (O2) to carbon dioxide (CO2) and water (H2O) and releasing energy.
Ç6H12O6 + O2 -> 6 CO2 + 6H2O + energy
The energy released in cellular respiration is stored in a substance called ATP (adenosine triphosphate), which spreads to all regions of the cell, providing energy for the most diverse cellular activities. The process of cellular respiration will be further explained in the Energy Metabolism section.