Peroxisomes!
Peroxisomes are a group of organelles that are found in the cytoplasm of all cells. Peroxisomes contain a variety of enzymes that convert hydrogen peroxide into water. some types of peroxisomes detoxify alcohol and other harmful compounds by transferring hydrogen from the poisons to molecules of oxygen, this process is called oxidation. Others are more important for their ability produce phospholipids, which are typically used in the formation of membranes. In order to do their job peroxisomes use a lot of oxygen.
http://micro.magnet.fsu.edu/cells/peroxisomes/images/peroxisomesfigure2.jpg
http://blogs.discovermagazine.com/notrocketscience/files/2011/04/Breast_stem_cells.jpg
http://micro.magnet.fsu.edu/cells/peroxisomes/images/peroxisomesfigure2.jpg
http://blogs.discovermagazine.com/notrocketscience/files/2011/04/Breast_stem_cells.jpg