The Endomembrane System

These flashcards summarize key concepts from a lecture on the Endomembrane System, including its components, functions, and processes involved in protein synthesis and trafficking.

Endomembrane System

A collection of membranes that include the endoplasmic reticulum, Golgi complex, vesicles, and lysosomes.

Endoplasmic Reticulum (ER)

A continuous network of flattened sacs and tubules through the cytoplasm of a eukaryotic cell, involved in protein synthesis.

Rough Endoplasmic Reticulum (Rough ER)

Characterized by ribosomes on its cytosolic side, involved in synthesizing membrane-bound and soluble proteins.

Smooth Endoplasmic Reticulum (Smooth ER)

Lacks ribosomes, involved in drug detoxification, metabolism of carbohydrates, calcium storage, and membrane biosynthesis.

Cotranslational Translocation

The process by which nascent polypeptides are targeted and transported into the ER lumen during protein synthesis.

Golgi Complex

A stack of membrane-bound cisternae responsible for processing, sorting, and packaging proteins and lipids from the ER.

Anterograde Transport

Movement of vesicles containing proteins from the ER to the Golgi or plasma membrane.

Retrograde Transport

Movement of vesicles from the Golgi back to the ER.

Vesicles

Small membrane-bound sacs that transport different molecules between membranes in the cell.

Endocytosis

The process by which cells internalize external materials by engulfing them in membrane-bound vesicles.

Exocytosis

The process by which vesicles fuse with the plasma membrane to release their contents outside the cell.

Lysosome

An organelle that contains digestive enzymes capable of degrading all major classes of biological macromolecules.

Coated Vesicles

Vesicles that are surrounded by a protein coat, involved in transporting proteins and lipids between organelles.

SNARE proteins

Proteins involved in the fusion of vesicles with target membranes, facilitating intracellular transport.

Receptor-Mediated Endocytosis

A form of endocytosis in which cells use receptors to internalize specific macromolecules.

Low-Density Lipoprotein (LDL)

A type of lipoprotein responsible for transporting cholesterol in the bloodstream, often associated with health risks when elevated.

Signal Sequence

A short peptide that directs the transport of a protein to the correct organelle or cellular membrane.

Quality Control in the ER

Processes that ensure only properly folded and assembled proteins proceed to the next stage of processing.

Clathrin

A protein that coats vesicles for transport, especially in endocytosis.