Endoplasmic Reticulum

Endoplasmic reticulum (ER) is a membranous labyrinth so extensive that it accounts for more than half the total membrane in many eukaryotic cells. The word endoplasmic means "within" the cytoplasm, and the word reticulum is derived from a word meaning "network." The ER consists of a network of membranous tubules and sacs called cisternae. The ER membrane separates its internal compartment, the cisternal space, from the cystosol. Because the ER membrane is continuous with the nuclear envelope, the space between the two membranes of the envelope is continuous with the cisternal space of the ER.

There are two specific regions of ER that are different in structure and function. The two forms are rough ER and smooth ER. The rough ER appears rough because of ribosomes. The ribosomes are attached to ER making appear bumpy. Smooth ER has its name simply beacuse its cytoplasmic surface does not contain ribosomes. Rough ER specializes in protein synthesis. The endoplasmic reticulum is a transport system. Protein molecules move from the rough ER into the smooth ER, which then sensds them enclosed within the vesicles usually to the Golgi complex.

The smooth ER of various cell types functions in diverse metabolic processes, including the synthesis of lipids, carbohydrate metabolism, and the detoxification of drugs and other poisons. Enzymes in the smooth ER are important to the synthesis of fats, phospolipids, steroids, and other lipids. The enzymes detoxify drugs and other poisons, especially in the liver cells. This makes it easier to flush the toxic out of the body.

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