Endoplasmaretikulumile

Endoplasmaretikulumile, commonly called the endoplasmic reticulum (ER) in many languages, is a extensive network of membranous tubules and sacs found in most eukaryotic cells. It forms a continuous system that is connected to the outer membrane of the nuclear envelope and pervades the cytoplasm. The ER lumen is the internal space enclosed by the membranes.

The organelle is organized into two main regions with distinct roles. Rough endoplasmic reticulum (RER) has ribosomes bound to its cytosolic surface, giving a studded appearance. It is the primary site of synthesis for proteins destined for secretion, incorporation into cellular membranes, or delivery to lysosomes. The ER assists protein folding and quality control, often using chaperone proteins and the unfolded protein response to manage misfolded proteins. Smooth endoplasmic reticulum (SER) lacks ribosomes and is involved in lipid synthesis, carbohydrate metabolism, and detoxification processes. It also plays a crucial role in calcium storage and release, which is important for various cellular signaling events.

Functions of the ER extend to membrane production and protein sorting. Newly synthesized proteins and lipids are packaged into vesicles and transported to the Golgi apparatus via the ER-Golgi intermediate compartment. The ER collaborates with cellular quality-control systems to dispose of defective proteins by targeting them for degradation. In secretory cells, the ER's capacity influences the rate of protein production and secretion.

Endoplasmaretikulumile is present in most eukaryotic cells, with abundance and structure varying by cell type. It is essential for cellular homeostasis, protein processing, membrane synthesis, and intracellular signaling.