The structure labelled X is rough endoplasmic reticulum. Eukaryotic cells have a network or reticulum of tiny tubular structures scattered in the cytoplasm that is called the endoplasmic reticulum (ER). The endoplasmic reticulum bearing ribosomes on their surface is called the rough endoplasmic reticulum (RER). RER is frequently observed in the cells actively involved in protein synthesis and secretion. The golgi apparatus principally performs the function of packaging materials to be delivered either to the intra-cellular targets or secreted outside the cell. Energy production is the function of mitochondria
