(Science: Cell Biology)
(1) A membrane-bounded organelle that occurs as labyrinthine, interconnected flattened sacs or tubules that is connected to the nuclear membrane, runs through the cytoplasm, and may well extend into the cell membrane.
The RER bears many ribosomes on its outer surface giving it a rough appearance; hence, its name. Since RER has ribosomes attached to its surface it is therefore involved in protein synthesis and secretion. It synthesizes and secretes serum proteins (such as albumin) in the liver, and hormones (such as insulin) and other substances (such as milk) in the glands.
The SER, on the other hand, does not have ribosomes on its surface. Its functions include synthesis of lipids, metabolism of carbohydrates and calcium concentration, drug detoxification, and attachment of receptors on cell membrane proteins. It is also involved in intracellular transport, such as the transport of the products of the RER to other cell parts like Golgi apparatus.
Related forms: ER (acronym).