The endoplasmic reticulum (ER) is a part of a transportation system of the eukaryotic cell, and has many other important functions such as protein folding. It is a type of organelle made up of two subunits – rough endoplasmic reticulum (RER), and smooth endoplasmic reticulum (SER). The endoplasmic reticulum is found in most eukaryotic cells and forms an interconnected network of flattened, membrane-enclosed sacs known as cisternae, and tubular structures in the SER. The membranes of the ER are continuous with the outer nuclear membrane. The endoplasmic reticulum is not found in red blood cells, or spermatozoa.
Micrograph of rough endoplasmic reticulum network around the nucleus (shown in the lower right-hand area of the picture). Dark small circles in the network are mitochondria.
Ca2+-antagonized transport into the endoplasmic reticulum (CaATiER) model
The eukaryotes constitute the domain of Eukarya or Eukaryota, organisms whose cells have a membrane-bound nucleus. All animals, plants, fungi, and many unicellular organisms are eukaryotes. They constitute a major group of life forms alongside the two groups of prokaryotes: the Bacteria and the Archaea. Eukaryotes represent a small minority of the number of organisms, but given their generally much larger size, their collective global biomass is much larger than that of prokaryotes.
Image: Rhodomonas salina CCMP 322
Image: Ranunculus asiaticus 4LEST
Image: Trypanosoma sp. PHIL 613 lores
Image: Chaos carolinensis Wilson 1900