1

 It is a specific type of endoplasmic reticulum, which surrounds the nucleus.  SER is found in both animal cells and plant cells.  Unlike RER, it is tubular in form.  Because it lacks ribosomes, it is known as smooth ER.  Large quantities of certain compounds such as Phenobarbital cause an increase in the amount of SER. 2

 The smooth ER is the site of synthesis of lipids, including phospholipids, which are major components of the plasma and internal membranes.  SER contains enzymes that function in the synthesis of steroid hormones.  The membranes of SER contain enzymes that catalyze a series of reactions to detoxify both lipid-soluble drugs and harmful products of metabolism, especially in the liver cells.  It functions in the regulation of calcium concentration, which is important for muscle contraction. 3

 The SER represents only a small portion of ER in most cells, but it is a prominent constituent in the cells of the adrenal cortex, and the cells of the liver.  It serves as a transport of proteins synthesized in the RER to the Golgi apparatus.  It also contains the enzyme glucose-6- phosphatase which is converted to glucose (This is a step in gluconeogenesis). 4

IN A PLANT CELLIN AN ANIMAL CELL 5