Working models for autophagy and the Cvt pathway in the yeast S. cerevisiae. Both pathways require a membrane nucleation step followed by the formation of double-membrane vesicles. The type of vesicles that are produced depends on the nutrient conditions. Autophagosomes (300 to 900 nm diameter) form during autophagy under conditions of nutrient deprivation. Cvt vesicles (140 to 160 nm diameter) are generated through the Cvt pathway under nutrient-rich conditions. The subsequent fusion of the vesicle with the vacuole membrane results in autophagic bodies or Cvt bodies that are ultimately degraded. The degradation process allows the precursor form of the resident hydrolase aminopeptidase I (prApe1) to be processed into its mature form (mApe1). While the biosynthetic Cvt pathway selectively packages and transports prApe1 under nutrient rich conditions, prApe1 is able to be transported through autophagy during starvation.