Cell Membrane vs Cell Wall
Every cell has a membrane — a thin lipid bilayer that surrounds the cytoplasm and controls what enters and leaves. Some cells (plants, fungi, bacteria, archaea) also have a cell wall outside the membrane: a rigid structural layer that gives the cell shape and strength. Animal cells have only the membrane; plant cells have both.
Last reviewed on 2026-10-03.
Quick Comparison
| Aspect | Cell Membrane | Cell Wall |
|---|---|---|
| Found in | Every cell | Plants, fungi, bacteria, archaea (not animal cells) |
| Position | Inside the cell wall (where one exists) | Outside the cell membrane |
| Composition | Lipid bilayer with embedded proteins | Plants: cellulose; Fungi: chitin; Bacteria: peptidoglycan |
| Permeability | Selectively permeable — actively controls passage | Fully permeable to most small molecules |
| Function | Controls what enters/exits; holds organelles inside | Provides structural support and protection |
| Flexibility | Flexible | Rigid |
| Replaceable? | Maintained by the cell | Maintained by the cell |
Key Differences
1. Universality
Every cell, in every form of life on Earth, has a cell membrane. It's the boundary that defines a cell as a cell.
Cell walls are present in plants, fungi, bacteria, and archaea — but not in animals or most protists. The presence and composition of a wall are characteristic features for identifying organisms.
2. Composition
The cell membrane is a phospholipid bilayer with embedded proteins (channels, transporters, receptors), cholesterol (in animal cells), and surface carbohydrates. The structure is mostly fluid; components diffuse laterally within it.
Cell wall composition varies dramatically by organism: plants use cellulose (the most abundant biopolymer on Earth); fungi use chitin (the same material as insect exoskeletons); bacteria use peptidoglycan; archaea use a variety of materials, often pseudopeptidoglycan.
3. Permeability
The cell membrane is selectively permeable. Small uncharged molecules (water, oxygen, CO2) pass freely; ions and larger molecules need specific channels or transporters. The cell expends energy to control what enters and leaves.
The cell wall, by contrast, is mostly a passive sieve. It allows water and small dissolved molecules through; it doesn't actively select for what passes. The membrane underneath does the active filtering.
4. Function
The cell membrane defines the cell's interior and exterior, controls transport, and houses receptors that sense the outside world. It's the active interface.
The cell wall is structural. It provides shape, mechanical support, and protection against bursting under turgor pressure. In bacteria it also provides structural rigidity that makes the cell resistant to environmental stress.
5. Mechanical properties
Cell membranes are flexible. Animal cells take many shapes; even plant-cell membranes mould to the wall.
Cell walls are rigid. Plant cells are essentially the shape their walls give them; the wall is what makes wood structural.
6. Why animals don't have walls
Animals trade structural rigidity for mobility and flexibility. Animal tissues need cells that can change shape, slide past each other, and respond to mechanical signals.
Plants trade flexibility for structural support without skeletons. The cell wall lets plants stand upright, transport water vertically, and grow large structures from small components.
When to Choose Each
Choose Cell Membrane if:
- Anywhere active transport, signal reception, or cellular communication matters.
- In animal physiology — every cell in the body has only a membrane.
- When discussing what passes in or out of cells (drugs, nutrients, waste).
Choose Cell Wall if:
- In plants — every plant cell has a wall, and walls together create wood, fibre, and structure.
- In bacteria — the wall is the target of many antibiotics (penicillin disrupts peptidoglycan synthesis).
- In fungi — chitin walls are part of what distinguishes them from plants.
Worked example
A plant cell sits in a salty solution. Water rushes out across the cell membrane (osmosis), but the cell wall prevents the cell from fully shrinking — it stays mostly the same shape, just losing turgor. An animal cell in the same solution has only a membrane to defend it; it shrinks and may rupture. The structural difference is exactly why plants and animals respond so differently to environmental water stress.
Common Mistakes
- "All cells have a cell wall." Animal cells don't. The presence of a wall is one of the first things distinguishing kingdoms.
- "The cell membrane and cell wall do the same job." Different jobs — the membrane controls passage; the wall provides structure.
- "All cell walls are made of cellulose." Only plants. Fungi use chitin; bacteria use peptidoglycan.
- "Cell walls block everything." They're mostly permeable to small molecules; the membrane underneath is the real gatekeeper.
Frequently Asked Questions
What is the main difference between the cell membrane and the cell wall?
The cell membrane is a thin, flexible lipid bilayer that controls what enters and leaves the cell; every cell has one. The cell wall is a rigid outer layer outside the membrane that gives support and protection; only plants, fungi, bacteria, archaea and many algae have one.
Do animal cells have a cell wall?
No. Animal cells have only a cell membrane. This lets them change shape and move, and their support comes from the cytoskeleton and, in many animals, a skeleton.
What are cell walls made of?
Plant cell walls are mainly cellulose; fungal walls contain chitin; bacterial walls are made of peptidoglycan. Archaea have different wall materials again.
Which is on the outside, the cell wall or the cell membrane?
In cells that have both, the cell wall is outside the cell membrane. The membrane sits just inside the wall, surrounding the cytoplasm.
What is the difference between the cell membrane and cytoplasm?
The cell membrane is the boundary of the cell; the cytoplasm is the jelly-like contents inside it (cytosol plus organelles, excluding the nucleus).