If you looked at heart cells, would you expect to see a lot of mitochondria

or only a few? Why?

Function of Mitochondria. Just as a car runs on gasoline, your cells run on ATP ... It's your heart muscle cells - with about 5,000 mitochondria per cell - that contain far more mitochondria than any other organ in body! That's because the constantly-beating heart works harder than any other organ in your body!