endoplasmic reticulum

American  

[en-doh-plaz-mik ri-tik-yuh-luhm] / ˈɛn doʊˌplæz mɪk rɪˈtɪk yə ləm /

noun

Cell Biology.

1. a network of tubular membranes within the cytoplasm of the cell, occurring either with a smooth surface smooth endoplasmic reticulum or studded with ribosomes rough endoplasmic reticulum, involved in the transport of materials.

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endoplasmic reticulum British  

noun

1. an extensive intracellular membrane system whose functions include synthesis and transport of lipids and, in regions where ribosomes are attached, of proteins

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endoplasmic reticulum Scientific  

/ ĕn′də-plăz′mĭk /

1. An organelle consisting of a network of membranes within the cytoplasm of eukaryotic cells that is important in protein synthesis and folding and is involved in the transport of cellular materials. The endoplasmic reticulum can be continuous in places with the membrane of the cell nucleus. The function of the endoplasmic reticulum can vary greatly with cell type, and even within the same cell it can have different functions depending on whether it is rough or smooth.

2. ◆ The rough endoplasmic reticulum is a series of connected flattened sacs that have many ribosomes on their outer surface. Rough endoplasmic reticulum 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.

3. ◆ The smooth endoplasmic reticulum is tubular in form and is involved in the synthesis of phospholipids, the main lipids in cell membranes. Smooth endoplasmic reticulum is the site of the breakdown of toxins and carcinogens in the liver, the conversion of cholesterol into steroids in the gonads and adrenal glands, and the release of calcium ions in the muscles, causing muscle contraction. The smooth endoplasmic reticulum also transports the products of the rough endoplasmic reticulum to other cell parts, notably the Golgi apparatus.

4. See more at cell

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Etymology

Origin of endoplasmic reticulum

First recorded in 1945–50

Example Sentences

One, called LCA, damaged T cell function by causing endoplasmic reticulum stress, while another, UDCA, boosted T cell performance and drew more immune cells to the liver.

From Science Daily • Oct. 17, 2025

ZIP7 is also the only zinc transporter found in the endoplasmic reticulum, a membranous structure where a cell makes proteins destined for the outer membrane of the cell or for secretion out of the cell.

From Science Daily • Apr. 30, 2024

The two proteins "sit" at the endoplasmic reticulum exit site, a place in the cell where materials like proteins are packaged and transported out the cell.

From Science Daily • Apr. 24, 2024

This allows the cytoskeleton to act as a highly dynamic intracellular wiring network to transmit ion-based information from the membrane to the intracellular organelles, including mitochondria, endoplasmic reticulum and the nucleus.

From Science Daily • Apr. 24, 2024

The cleavage of SREBP-1c occurs in the endoplasmic reticulum, with the rhomboid protease RHBDL4, located in the ER membrane, identified as a new cleavage enzyme for SREBP-1c.

From Science Daily • Jan. 13, 2024