Pancreatic acinar cell. Coloured high resolution scanning electron micrograph (SEM) of an acinar cell from the pancreas. At lower left is the nucleus (blue) with its nucleolus (red circle). The nucleus contains the genetic information. Coloured green are mitochondria, the sources of energy within the cell. The brown, white and orange coloured circles are zymogen granules. Zymogen is an inactive form of a digestive enzyme. The cell is filled with a network of densely folded membranes of rough endoplasmic reticulum (purple). These membranes are the sites of protein synthesis. Magnification unknown.