---
title: "Rough Endoplasmic Reticulum — AP Bio Definition & Guide"
description: "The rough ER is the ribosome-studded organelle that builds and folds proteins, a key example of how eukaryotic cells compartmentalize functions inside membranes."
canonical: "https://fiveable.me/ap-bio/key-terms/rough-endoplasmic-reticulum"
type: "key-term"
subject: "AP Biology"
---

# Rough Endoplasmic Reticulum — AP Bio Definition & Guide

## Definition

The rough endoplasmic reticulum is an organelle found in eukaryotic cells. Its primary function is to produce proteins for the rest of the cell to function. It's called 'rough' because it's studded with ribosomes.

## Related Study Guides

- [2.10 Origins of Cell Compartmentalization](/ap-bio/unit-2/cell-compartmentalization/study-guide/HRfoDYQgTXrvyzemUlwu)

## Review

### Related Terms

- [Smooth Endoplasmic Reticulum](/ap-bio/key-terms/smooth-endoplasmic-reticulum): This is similar to the rough ER but it's smooth because it doesn't have ribosomes. It synthesizes lipids and detoxifies certain chemicals.
- [Golgi Apparatus](/ap-bio/key-terms/golgi-apparatus): This organelle processes and packages proteins synthesized in the rough ER, much like a food packaging and delivery service.
- Protein Folding: This is the process by which a protein structure assumes its functional shape or conformation. It happens within the Rough ER.