All cells have organelles ("little organs") that help them do the chemistry of their living. As there are many different tissues in the body, so are there many different cells, which can contain different organelles. One type of organelle are the mitochondria, the "powerhouse" of the cell, which chemically produces energy-rich ATP through respiration. Some cells in a given tissue only have one mitochondria; in the case of muscle, because it requires so much energy to contract, a typical animal muscle cell can have upwards of 2000 mitochondria. Plant cells, which also require energy, have a different energy producing chemistry through photosynthesis, and have chloroplasts instead of mitochondria.