Both animal and plant cells depend on autophagy in which damaged or superfluous cell material is removed. The degradation of substrates is done by proteins. In animals, it takes place in a cell organelle called the lysosome and in plants and yeasts in the vacuole. Initially, the degradation proteins are not located in the vacuole or lysosome; rather, they must be conveyed by transport receptors on small vesicles to their site of action.