Why it is important
mitochondria is the mass producer of ATP which is the energy for cells to reproduce and make Daughter cells. Some of the other cells produce ATP but not as much as mitochondria. they also are able to act on their own and have their own genetic material, and the machinery to manufacture their own RNA's and proteins. but the downside is that nothing follows the Mitochondria DNA or needs in order to function. Mitochondria also has the ability to signal other cells if something is wrong .
okay lets say Mitochondria gets kicked out of the cell then what would happen? Well for one the cell would functon normally with the nucoules in charge untill they needed to reproduce. Now they could but not that much as they would be able to if they had the Mitochondria. because they would have little of ATP the ingredient for reproduction. So there would still be cells but not that much without Mitochondria's help so basically wirhout it there wouldn't be a lot of cells