endoplasmic reticulum membrane

Definition

Target type: cellularcomponent

The lipid bilayer surrounding the endoplasmic reticulum. [GOC:mah]

The endoplasmic reticulum (ER) membrane is a complex and dynamic organelle that plays a critical role in protein synthesis, folding, and trafficking, lipid biosynthesis, and calcium signaling. It is a continuous network of interconnected flattened sacs, tubules, and vesicles that extends throughout the cytoplasm of eukaryotic cells. The ER membrane encloses a lumen, which is distinct from the cytosol and contains a specialized environment for protein and lipid processing.

The ER membrane is composed of a phospholipid bilayer, similar to the plasma membrane, but with a unique lipid composition. It is enriched in phospholipids such as phosphatidylcholine, phosphatidylethanolamine, and phosphatidylinositol, which contribute to its fluidity and structural integrity. The ER membrane also contains a variety of integral membrane proteins that are essential for its diverse functions. These proteins include:

**Transmembrane proteins:** These proteins span the ER membrane and facilitate the transport of molecules across the membrane. They include:

* **Translocons:** These protein complexes mediate the movement of newly synthesized proteins from the cytosol into the ER lumen.
* **Chaperones:** These proteins assist in the proper folding of proteins within the ER lumen.
* **Glycosyltransferases:** These enzymes add sugar moieties to proteins, a process known as glycosylation.
* **Lipid synthesis enzymes:** These enzymes catalyze the synthesis of various lipids, including phospholipids, cholesterol, and steroid hormones.
* **Calcium channels:** These proteins regulate the flow of calcium ions across the ER membrane, playing a key role in calcium signaling.

**Peripheral membrane proteins:** These proteins associate with the ER membrane through interactions with lipid head groups or transmembrane proteins. They include:

* **Protein kinases and phosphatases:** These enzymes modify the activity of other ER membrane proteins through phosphorylation or dephosphorylation.
* **Scaffolding proteins:** These proteins provide structural support and organize the ER membrane into specific domains.

The ER membrane is highly dynamic and can undergo extensive remodeling in response to cellular needs. Its structure and composition are constantly changing as proteins are synthesized, transported, and modified within the ER lumen. The ER membrane is also involved in the formation of other organelles, such as the Golgi apparatus and lysosomes. Its intricate network and diverse functions make it an essential component of eukaryotic cells, playing a central role in maintaining cellular homeostasis and carrying out various cellular processes.'
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Proteins (428)

Compounds (2,981)