The chondrioma of a cell is the set of 300 to 800 mitochondria (from 1000 to 3000 in muscle cells, 2500 of which in a parenchymal cell of the liver or, which is a smooth muscle) which constitute up to 25% of the cell mass.
Very numerous in young cells and / or very active, which require a lot of energy (like spermatozoa), mitochondria are organelles because they constitute functional units of the cell: they are the "energy factories". Omnipresent in any animal or plant cell, mitochondria exist even in anucleate blood thrombocytes.