Smooth endoplasmic reticulum
(A part of) endoplasmic reticulum that is tubular in form (rather than sheet-like) and lacks ribosomes. Its functions include lipid synthesis, carbohydrate metabolism, calcium concentration, drug detoxification, and attachment of receptors on cell membrane proteins.
It is seen connected to the nuclear envelope, and consists of tubules and vesicles that branch forming a network to increase surface area for the action or storage of key enzymes. It contains the enzyme Glucose-6-phosphatase (which converts glucose-6-phosphate to glucose), a step in gluconeogenesis. A specialized form of SER (called sarcoplasmic reticulum) occurs in muscle cells where calcium ions are stored. It is also abundant in hepatocytes to process and detoxify lipophilic drugs.