Endoplasmic reticulum

The endoplasmic reticulum is a membrane network in eukaryotic cells that synthesizes and processes proteins and lipids and helps regulate calcium storage.

Rough endoplasmic reticulum: The ribosome-studded region of the endoplasmic reticulum where many secreted and membrane proteins are synthesized. Ribosomes on this region feed newly made proteins into its lumen or membrane.
Eukaryotic cell: A cell whose genetic material is enclosed in a nucleus and whose interior contains membrane-bound compartments. The ER is one of the defining membrane-bound compartments of eukaryotic cells.
Secretory pathway: The route by which proteins and lipids move from the endoplasmic reticulum through the Golgi apparatus to cellular destinations. The ER supplies the entry point for proteins and lipids moving through this pathway.
Endoplasmic reticulum stress: A condition in which the endoplasmic reticulum cannot adequately fold or process its protein load. Persistent folding demands can disrupt the ER functions that maintain cellular health.
Smooth endoplasmic reticulum: The ribosome-free region of the endoplasmic reticulum involved in lipid metabolism, detoxification, and calcium storage. This region emphasizes lipid production and calcium handling rather than ribosome-bound protein synthesis.
Biological membrane: A selectively permeable lipid bilayer containing proteins that separates cellular compartments from their surroundings. The ER's continuous sheets and tubules are built from this basic structure.
Golgi apparatus: A eukaryotic organelle that modifies, sorts, and packages proteins and lipids received from the endoplasmic reticulum. It receives ER cargo and continues its processing and distribution.
Cystic fibrosis: An inherited disease caused by CFTR gene variants that impair salt and water transport in epithelial tissues. Some CFTR variants are retained and degraded after failing ER folding quality control.
Signal recognition particle: A ribonucleoprotein complex that directs translating ribosomes to the endoplasmic reticulum when they make a targeting signal. It brings many nascent secretory and membrane proteins to the rough ER.
Ribosome: A molecular complex of RNA and proteins that translates messenger RNA into a polypeptide. Ribosomes attached to the rough ER synthesize proteins destined for membranes or secretion.

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