---
title: "Endoplasmic Reticulum — AP Bio Definition & Exam Guide"
description: "The endoplasmic reticulum is the cell's protein and lipid factory. Learn how the ER ties to membrane surface area, protein synthesis, and the secretory pathway on the AP Bio exam."
canonical: "https://fiveable.me/ap-bio/key-terms/endoplasmic-reticulum"
type: "key-term"
subject: "AP Biology"
---

# Endoplasmic Reticulum — AP Bio Definition & Exam Guide

## Definition

The endoplasmic reticulum (ER) is an organelle within cells that serves as a production and packaging system. It's involved in protein synthesis, lipid metabolism, and detoxification processes.

## Related Study Guides

- [2.2 Cell Size](/ap-bio/unit-2/cell-structure-function/study-guide/znjrRPCY6596o2nWt05n)

## Review

### Related Terms

- Rough ER: A type of endoplasmic reticulum covered with ribosomes, involved in protein synthesis and quality control.
- Smooth ER: A type of endoplasmic reticulum without ribosomes; its functions include lipid synthesis and drug detoxification.
- [Golgi Apparatus](/ap-bio/key-terms/golgi-apparatus): An organelle responsible for transporting, modifying, and packaging proteins and lipids to their targeted destinations.