Mitochondria are are organelles that floats freely in the cell.They keep the cells fully energised by acting like a digestive system
which takes in nutrients, breaks them down, and creates energy rich
molecules for the cell.
Some cells have several thousand mitochondria while others have none. Muscle cells
need a lot of energy so they have loads of mitochondria. Sometimes a mitochondria can grow larger or combine with other
mitochondria depending on the needs of the cell.