Cisternae are the flattened, disc-like, membrane-bound sacs that comprise the Golgi apparatus (also called Golgi complex or Golgi body). They are stacked together and function in processing, packaging, and modifying proteins and lipids synthesized in the endoplasmic reticulum. The Golgi apparatus is not found in mitochondria (powerhouse of cell), chloroplasts (site of photosynthesis), or nucleolus (site of ribosome synthesis).