---
title: "Cell Wall — AP Biology Definition & Exam Guide"
description: "The cell wall is a rigid polysaccharide layer outside the plasma membrane that protects cells from osmotic lysis. See how it's tested in AP Bio Unit 2."
canonical: "https://fiveable.me/ap-bio/key-terms/cell-wall"
type: "key-term"
subject: "AP Biology"
---

# Cell Wall — AP Biology Definition & Exam Guide

## Definition

The cell wall is a rigid layer of polysaccharides lying outside the plasma membrane of the cells of plants, fungi, and bacteria. In algae and higher plants, it consists mainly of cellulose.

## Related Study Guides

- [2.8 Mechanisms of Transport](/ap-bio/unit-2/tonicity-osmoregulation/study-guide/CCENUydXNVb7K4P7ikp7)
- [Origins of Cell Compartmentalization Review](/ap-bio/unit-2/origins-of-compartmentalization/study-guide/GC84zJJwIDYFWwSzFPNy)

## Review

### Related Terms

- [Cellulose](/ap-bio/key-terms/cellulose): A complex carbohydrate that forms the main constituent of the cell wall in most plants and is important in the manufacture of numerous products, such as paper, textiles, pharmaceuticals, and explosives.
- [Plasma Membrane](/ap-bio/key-terms/plasma-membrane): The semipermeable membrane surrounding the cytoplasm of a cell that controls what enters or leaves a cell.
- [Polysaccharide](/ap-bio/key-terms/polysaccharide): A carbohydrate whose molecules consist of a number of sugar molecules bonded together; they are an important component in plant's structural building material.