endoplasmatisk

Endoplasmatisk is a term used in cell biology to refer to the endoplasmatic reticulum (ER), a large, membrane-bound organelle in most eukaryotic cells. The ER forms an interconnected network of tubules and flattened sacs that is continuous with the outer nuclear envelope and extends throughout the cytoplasm. It provides a surface and internal space (the ER lumen) for various essential biosynthetic processes.

Two principal forms are commonly described: rough endoplasmatisk retikel and smooth endoplasmatisk retikel. The rough ER bears ribosomes on its cytosolic surface and is the primary site of synthesis for secreted and membrane proteins. Newly synthesized polypeptides are translocated into the ER lumen, where they fold and undergo initial post-translational modifications. The smooth ER lacks ribosomes and is involved in lipid biosynthesis, including phospholipids and cholesterol, as well as detoxification reactions in some tissues. It also contributes to calcium storage and homeostasis.

Distribution and variation of the ER reflect cell function. Secretory cells, such as those in the pancreas, often exhibit extensive rough ER, while hepatocytes display prominent smooth ER for detoxification tasks. In muscle cells, a specialized form called the sarcoplasmic reticulum regulates calcium release during contraction.

Function and significance include protein folding and quality control, trafficking of proteins to the Golgi apparatus, lipid synthesis, and calcium storage. Disruptions in ER function can lead to cellular stress responses and contribute to various diseases.

Origins of the term: Endoplasmatisk derives from endoplasm (within the cytoplasm) and plasma, reflecting its location within the cytoplasmic region of the cell. The term is used in several languages to describe the endoplasmic reticulum.