Rough Endoplasmic Reticulum

∞ generated and posted on 2016.08.26 ∞

Endomembrane system member associated with synthesis of membrane proteins along with synthesis of secreted proteins.

The endoplasmic reticulum is so named because it consists of reticulating membranes shaped like flattened tubes, called cisternae, that are found within the cell.

They are "rough" because ribosomes – which are fairly large, globular structures – are found on their outside, providing a grainy appearance (and contrasting smooth endoplasmic reticulum in appearance, which lack ribosomes on their surface).

Membrane proteins are those that end up being embedded within membranes, giving rise to the fluid mosaic nature of membranes. Secreted proteins exit the cell entirely.

Note that a third category of proteins produced in the rough endoplasmic reticulum also exists and these are proteins that remain in the endomembrane lumen (of various organelles, e.g., lysosomes), that is, which are contained by but not physically attached to endomembranes. All are synthesized in association with the rough endoplasmic reticulum in eukaryotes.