Endoplasmic reticulum

Electron micrograph of rough endoplasmic reticulum network around the nucleus (shown in lower right-hand side of the picture). Dark small circles in the network are mitochondria.

1 Nucleus 2 Nuclear pore 3 Rough endoplasmic reticulum (RER) 4 Smooth endoplasmic reticulum (SER) 5 Ribosome on the rough ER 6 Proteins that are transported 7 Transport vesicle 8 Golgi apparatus 9 Cis face of the Golgi apparatus 10 Trans face of the Golgi apparatus 11 Cisternae of the Golgi apparatus

Endoplasmic reticulum (ER) is a cellular organelle. It is the transport network for molecules going to specific places, as compared to molecules that float freely in the cytoplasm. The endoplasmic reticulum is in cells that have a nucleus: in eukaryote cells but not in prokaryote cells. It takes these forms:

Rough endoplasmic reticulum (RER), so called because it is studded with ribosomes, and secretes proteins into the cytoplasm.
Smooth endoplasmic reticulum (SER). Among its functions is the production of proteins and steroids, the maintenance of plasma membranes, and a pathway for molecules to move along.

Similar to the ER is the sarcoplasmic reticulum (SR) found only in muscle cells. The SR stores and pumps calcium ions. The SR contains large stores of calcium, which it releases when the muscle cell is stimulated.^[1] Another type of cytoplasmic network is the plate-like Golgi apparatus.

The lacey membranes of the endoplasmic reticulum were first seen in 1945 by scientists using an electron microscope.^[2]

Endoplasmic Reticulum Media

3D rendering of endoplasmic reticulum
A 2-minute animation showing how a protein destined for the secretory pathway is synthesized and secreted into the rough endoplasmic reticulum, which appears at the upper right approximately halfway through the animation
Electron micrograph showing smooth ER (arrow) in mouse tissue, at 110,510× magnification
Skeletal muscle fiber, with sarcoplasmic reticulum colored in blue
Ca2+-antagonized transport into the endoplasmic reticulum (CaATiER) model

References

↑ Toyoshima C.; et al. (2000). "Crystal structure of the calcium pump of sarcoplasmic reticulum at 2.6 A resolution". Nature. 405 (6787): 647–55. doi:10.1038/35015017. PMID 10864315. S2CID 4316039.
↑ Porter K.R; Claude A. & Fullam E.F. (1945). "A study of tissue culture cells by electron microscopy". J Exp Med. 81 (3): 233–246. doi:10.1084/jem.81.3.233. PMC 2135493. PMID 19871454.{{cite journal}}: CS1 maint: multiple names: authors list (link)

[sarcoplasmic-1] Toyoshima C.; et al. (2000). "Crystal structure of the calcium pump of sarcoplasmic reticulum at 2.6 A resolution". Nature. 405 (6787): 647–55. doi:10.1038/35015017. PMID 10864315. S2CID 4316039.

[FirstER-2] Porter K.R; Claude A. & Fullam E.F. (1945). "A study of tissue culture cells by electron microscopy". J Exp Med. 81 (3): 233–246. doi:10.1084/jem.81.3.233. PMC 2135493. PMID 19871454.{{cite journal}}: CS1 maint: multiple names: authors list (link)

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